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Wikipedia

Road

January 21, 2023

For other uses, see Road (disambiguation).

A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation.

There are many types of roads, including parkways, avenues, controlled-access highways (freeways, motorways, and expressways), tollways, interstates, highways, thoroughfares, and local roads.

The primary features of roads include lanes, sidewalks (pavement), roadways (carriageways), medians, shoulders, verges, bike paths (cycle paths), and shared-use paths.

Definitions

 
A bricked road in Bangladesh
 
A gravel road in Namibia

Historically many roads were simply recognizable routes without any formal construction or some maintenance.[1]

The Organization for Economic Co-operation and Development (OECD) defines a road as "a line of communication (travelled way) using a stabilized base other than rails or air strips open to public traffic, primarily for the use of road motor vehicles running on their own wheels", which includes "bridges, tunnels, supporting structures, junctions, crossings, interchanges, and toll roads, but not cycle paths".[2]

The Eurostat, ITF and UNECE Glossary for Transport Statistics Illustrated defines a road as a "Line of communication (traveled way) open to public traffic, primarily for the use of road motor vehicles, using a stabilized base other than rails or air strips. [...] Included are paved roads and other roads with a stabilized base, e.g. gravel roads. Roads also cover streets, bridges, tunnels, supporting structures, junctions, crossings and interchanges. Toll roads are also included. Excluded are dedicated cycle lanes."[3]

The 1968 Vienna Convention on Road Traffic defines a road as the entire surface of any way or street open to public traffic.[4]

In urban areas roads may diverge through a city or village and be named as streets, serving a dual function as urban space easement and route.[5] Modern roads are normally smoothed, paved, or otherwise prepared to allow easy travel.[6]

Australia

See also: Highways in Australia

Part 2, Division 1, clauses 11-13 of the National Transport Commission Regulations 2006 defines a road in Australia as 'an area that is open to or used by the public and is developed for, or has as one of its main uses, the driving or riding of motor vehicles.'[7]

Further, it defines a shoulder (typical an area of the road outside the edge line, or the curb) and a road-related area which includes green areas separating roads, areas designated for cyclists and areas generally accessible to the public for driving, riding or parking vehicles.

New Zealand

In New Zealand, the definition of a road is broad in common law[8] where the statutory definition includes areas the public has access to, by right or not.[9] Beaches, publicly accessible car parks and yards (even if privately owned), river beds, road shoulders (verges), wharves and bridges are included.[10] However, the definition of a road for insurance purposes may be restricted to reduce risk.

United Kingdom

In the United Kingdom The Highway Code details rules for "road users", but there is some ambiguity between the terms highway and road.[11] For the purposes of the English law, Highways Act 1980, which covers England and Wales but not Scotland or Northern Ireland, road is "any length of highway or of any other road to which the public has access, and includes bridges over which a road passes".[12] This includes footpaths, bridleways and cycle tracks, and also road and driveways on private land and many car parks.[13] Vehicle Excise Duty, a road use tax, is payable on some vehicles used on the public road.[13]

The definition of a road depends on the definition of a highway; there is no formal definition for a highway in the relevant Act. A 1984 ruling said "the land over which a public right of way exists is known as a highway; and although most highways have been made up into roads, and most easements of way exist over footpaths, the presence or absence of a made road has nothing to do with the distinction.[14][15] Another legal view is that while a highway historically included footpaths, bridleways, driftways, etc., it can now be used to mean those ways that allow the movement of motor vehicles, and the term rights of way can be used to cover the wider usage.[16]

United States

In the United States, laws distinguish between public roads, which are open to public use,[17] and private roads, which are privately controlled.[18]

History

Main article: History of road transport
Further information: Gravel road and Trail
 
Transfăgărășan called "the best road in the world" by Top Gear[19]
 
The Porta Rosa, a Greek street dating from the 3rd to 4th century BC in Velia, with a paved surface and gutters
 
A paved Roman road in Pompeii
 
Old tractor road over farmland, Ystad, Sweden
 
Ancient Sassanid Era Pathway in Behbahan, Persia
 
Ancient Cobblestoned Road in Behbahan

The assertion that the first pathways were the trails made by animals has not been universally accepted; in many cases animals do not follow constant paths.[1] Some believe that some roads originated from following animal trails.[20][21] The Icknield Way may exemplify this type of road origination, where human and animal both selected the same natural line.[22] By about 10,000 BC human travelers used rough roads/pathways.[1]

  • The world's oldest known paved road was constructed in Egypt some time between 2600 and 2200 BC.[23]
  • Stone-paved streets appear in the city of Ur in the Middle East dating back to 4000 BC.[1]
  • Corduroy roads (log roads) are found dating to 4000 BC in Glastonbury, England.[1]
  • The Sweet Track, a timber track causeway in England, is one of the oldest engineered roads discovered and the oldest timber trackway discovered in Northern Europe. Built in winter 3807 BC or spring 3806 BC, (tree-ring dating – dendrochronology – enabled very precise dating). It was claimed to be the oldest road in the world[24][25] until the 2009 discovery of a 6,000-year-old trackway in Plumstead, London.[26][27]
  • Brick-paved streets appeared in India as early as 3000 BC.[1]
  • c. 1995 BC: an early subdividing of roadways evidenced with sidewalks built in Anatolia.[28]
  • In 500 BC, Darius I the Great started an extensive road system for the Achaemenid Empire (Persia), including the Royal Road, which was one of the finest highways of its time,[29] connecting Sardis (the westernmost major city of the empire) to Susa. The road remained in use after Roman times. These road systems reached as far east as Bactria and India.[30]
  • In ancient times, transport by river was far easier and faster than transport by road,[25] especially considering the cost of road construction and the difference in carrying capacity between carts and river barges. A hybrid of road transport and ship transport beginning in about 1740 is the horse-drawn boat in which the horse follows a cleared path along the river bank.[31][32]
  • From about 312 BC, the Roman Empire built straight[33] strong stone Roman roads throughout Europe and North Africa, in support of its military campaigns. At its peak the Roman Empire was connected by 29 major roads moving out from Rome and covering 78,000 kilometers or 52,964 Roman miles of paved roads.[25]
  • In the 8th century AD, many roads were built throughout the Arab Empire. The most sophisticated roads were those in Baghdad, which were paved with tar. Tar was derived from petroleum, accessed from oil fields in the region, through the chemical process of destructive distillation.[34]
  • The Highways Act 1555 in Britain transferred responsibility for maintaining roads from government to local parishes.[25] This resulted in a poor and variable state of roads. To remedy this, the first of the turnpike trusts was established around 1706, to build good roads and collect tolls from passing vehicles. Eventually there were approximately 1,100 trusts in Britain and some 36,800 km (22,870 miles) of engineered roads.[25] The Rebecca Riots in Carmarthenshire and Rhayader from 1839 to 1844 contributed to a Royal Commission that led to the demise of the system in 1844,[35] which coincided with the development of the UK railway system.
  • In the late-19th century roading engineers began to cater for cyclists by building separate lanes alongside roadways.
  • From the beginning of the 20th century, roads were increasingly built for tourism and also to create jobs. A typical example of the stimulation of tourism is the Great Dolomite Road, while the creation of the panoramic coastal road Strada Costiera between Duino and Barcola in 1928 was very much focused on creating jobs.[36][37]

Design

 
A highway in Tampere (Finland)

Road design is part of highway engineering. Structural road design is designing a road for the environment in order to extend its longevity and reduce maintenance. The Shell pavement design method is used in many countries for the design of new asphalt roadsides.

Terminology

Main article: Glossary of road transport terms
Adverse camber
Where a road slopes towards the outside of a bend, increasing the likelihood that vehicles travelling at speed will skid or topple. Usually only a temporary situation during road maintenance.
Alignment
The route of the road, defined as a series of horizontal tangents and curves.
All-weather road
Unpaved road that is constructed of a material that does not create mud during rainfall.
Banked turn
Belisha Beacon
An orange globe, lit at night, used to highlight a pedestrian crossing
Bicycle boulevard
A street that allows local vehicle traffic, but is prioritized for bicycles and other non-motorized travel
 
A beach road (Newcastle, NSW, Australia)
Bollard
Rigid posts that can be arranged in a line to close a road or path to vehicles above a certain width
Byway
Highway over which the public have a right to travel for vehicular and other kinds of traffic, but is used mainly as a footpath or bridleway
Bypass
Road that avoids or "bypasses" a built-up area, town, or village
Bottleneck
Section of a road with a carrying capacity substantially below that of other sections of the same road
Botts' dots
Non-reflective raised pavement marker used on roads
Camber (or crown)
The slope of the road surface downwards away from the centre of the road, so that surface water can flow freely to the edge of the carriageway, or on bends angling of the surface to lean traffic 'into the bend' reducing the chance of a skid.
Cant
Another name for cross slope or camber
Carriageway
Part of the road intended for the movement of road motor vehicles; the parts of the road which form a shoulder for the lower or upper layers of the road surface are not part of the roadway, nor are those parts of the road intended for the circulation of road vehicles which are not self-propelled or for the parking of vehicles.[3]
Cat's eye
Reflective raised pavement marker used on roads
Chicane
Sequence of tight serpentine curves (usually an S-shape curve or a bus stop)
Chipseal
Road surface composed of a thin layer of crushed stone 'chips' and asphalt emulsion. It seals the surface and protects it from weather, but provides no structural strength. It is cheaper than asphalt concrete or concrete. In the United States, it is usually only used on low volume rural roads
Corniche
Road on the side of a cliff or mountain, with the ground rising on one side and falling away on the other
Cross slope
The slope of the pavement, expressed as units of rise per unit of run, or as a percentage
Curb (kerb)
A raised edge at the side of the roadway.
Curb extension
(also kerb extension, bulb-out, nib, elephant ear, curb bulge and blister) Traffic calming measure, intended to slow the speed of traffic and increase driver awareness, particularly in built-up and residential neighborhoods.
Cycle lane
Part of a carriageway designated for cycles and distinguished from the rest of the carriageway by longitudinal road markings. Mopeds may also be allowed to use a cycle lane.[3]
Cycle track
Independent road or part of a road designated for cycles and sign-posted as such. A cycle track is separated from other roads or other parts of the same road by structural means. Mopeds may also be allowed to use the cycle track.[3]
Cycling infrastructure
Cycling-friendly infrastructure integrated into the roadway or in its own right of way
Drainage gradient
Farm-to-market road
A state road or county road that connects rural or agricultural areas to market towns.
Fork
(literally "fork in the road") Type of intersection where a road splits
Grade
Longitudinal slope
Green lane
(UK) Unsurfaced road, may be so infrequently used that vegetation colonises freely, hence 'green'. Many green lanes are ancient routes that have existed for millennia.
Guide rail
Prevents vehicles from veering off the road into oncoming traffic, crashing against solid objects or falling from a road. Also called a guard rail or traffic barrier.
Gutter
A drainage channel usually at the edge of the road or along a median.
Interstate Highway System (United States)
System of Interstate and Defense Highways
Lane
One of the longitudinal strips into which a carriageway is divisible, whether or not defined by longitudinal road markings, which is wide enough for one moving line of motor vehicles other than motorcycles.[3]
Layby (Pullout, pull-off)
A paved area beside a main road where cars can stop temporarily to let another car pass.
Loose chippings
The hazard of stone chippings that have come loose
Median
On dual carriageway roads, including controlled-access highways, divided highways and many limited-access roads, the central reservation (British English), median (North American English), median strip (North American English and Australian English), neutral ground [Louisiana English] or central nature strip (Australian English): Area that separates opposing lanes of traffic
Motorway
(Europe) (Freeways in the US, Special road in the UK) Road, specially designed and built for motor traffic, which does not serve properties bordering on it, with separate carriageways for traffic in two directions, with no crossings at the same level (road, railway, tramway track, or footpath) and sign-posted as a motorway and is reserved for specific categories of road motor vehicles.[3]
Mountain pass
A relatively low-level route through a range of mountains
Milestone
One of a series of numbered markers placed along a road, often at regular intervals, showing the distance to destinations.
National Highway
Road built and maintained by a national authority.
Pavement
The road regarded as a geoconstruction. In the UK the term is road surface and the pavement is a pedestrian walkway alongside the road.
Pedestrian crossing
Designated point on a road where road marking or other means helps pedestrians cross safely
Pelican crossing
(officially Pelicon crossing) (UK) A PEdestrian LIght CONtrolled crossing.
Private highway
Highway owned and operated for profit by private industry
Private road
Road owned and maintained by a private individual, organization, or company rather than by a government
Profile
The vertical alignment of a road, expressed as a series of grades, connected by parabolic curves.
Protected Intersections for Bicycles
A much safer design with a corner refuge island, a setback crossing of the pedestrians and cyclists, generally between 1.5–7 metres of setback, a forward stop bar, which allows cyclists to stop for a traffic light well ahead of motor traffic who must stop behind the crosswalk. Separate signal staging or at least an advance green for cyclists and pedestrians is used to give cyclists and pedestrians no conflicts or a head start over traffic. The design makes a right turn on red, and sometimes left on red depending on the geometry of the intersection in question, possible in many cases, often without stopping.[38]
Protected Bicycle Path
Cyclists ideally have a protected bike lane on separated by a concrete median with splay kerbs if possible, and have a protected bike lane width of at least 2 metres if possible (one way). In the Netherlands, most one-way cycle paths are at least 2.5 metres wide.[39]
Public space
Place where anyone has a right to come without being excluded because of economic or social conditions
Ranch road
U.S. road that connects rural and agricultural areas to market towns
Road number
Often assigned to identify a stretch of public roads – often dependent on the type of road, with numbers differentiating between interstates, motorways, arterial thoroughfares, etc.
Road-traffic safety
Process to reduce the harm (deaths, injuries, and property damage) that result from vehicle crashes on public roads
Roadworks
Part or all of the road is occupied for work or maintenance
Roughness
Deviations from a true planar pavement surface, which affects vehicle suspension deflection, dynamic loading, ride quality, surface drainage and winter operations. Roughness have wavelengths ranging from 500 mm up to some 40 m. The upper limit may be as high as 350 m when considering motion sickness aspects; motion sickness is generated by motion with down to 0.1 Hz frequency; in an ambulance car driving 78 mph (126 km/h), waves with up to 350 m will excite motion sickness.
Roundabout
A road junction where typically three or more roads are joined by a circular section of road. Traffic 'on the roundabout' has priority over traffic on approach roads, unless indicated otherwise. In countries where traffic drives on the left the roundabout is traveled in a clockwise direction. Also known as an island in parts of the UK.
Segregated Bicycle Path
Cyclists ideally have a protected bike lane separated by a concrete median with splay kerbs if possible, and have a protected bike lane width of at least 2 meters if possible (one way). In the Netherlands, most one-way cycle paths are at least 2.5 metres wide.[39]
Shoulder (also hard shoulder)
A clear, level area to the side of the roadway available for stopping if needed.
State highway
Road numbered by the state, falling below numbered national highways (like U.S. Routes) in the hierarchy or a road maintained by the state, including nationally numbered highways
Traffic
Pedestrians, ridden or herded animals, vehicles, bicycles, and other conveyances using any road for purposes of travel.[40]
Texture (roads)
Deviations from a true planar pavement surface, which affects the interaction between road and tire. Microtexture have wavelengths below 0.5 mm, Macrotexture below 50 mm and Megatexture below 500 mm.
Traffic calming
Set of strategies used by urban planners and traffic engineers to slow down or reduce motor vehicle traffic, thereby improving safety for pedestrians and bicyclists and improving the environment for residents
Traffic island
(UK) A small raised area used to help define the traffic flow, which may also act as a refuge for pedestrians crossing the carriageway or a location for signs, barriers or lights – a synonym for roundabout in some parts of the UK
Traffic light
Also known as a traffic signal, stop light, stop-and-go lights – a signaling device at a road intersection, pedestrian crossing, or other location that assigns right of way to different approaches to an intersection
Zebra crossing (UK)
A pedestrian crossing marked by black and white stripes on the carriageway

Construction

See also: Roadworks, Macadam, and Track bed
 
Layers in the construction of a mortarless pavement: A.) Subgrade B.) Subbase C.) Base course D.) Paver base E.) Pavers F.) Fine-grained sand

In transport engineering, subgrade is the native material underneath a constructed road.

[[File:Burbank Ave I-5 overpass under construction in Burbank, California.JPG|thumb|Overpass under construction over Interstate 5 in [[Burbank, California], USA][41][42]]] [[File:us land survey officer.jpg|thumb|Surveyor at work with a leveling instrument]]

 
Asphalt layer and Hamm road roller
 
Sub-base layer composed of cement-based material being applied during construction of the M8 motorway in Ireland
 
Road construction in Myanmar
 
Clearing rocks from mountain road in Spiti

Road construction requires the creation of an engineered continuous right-of-way or roadbed, overcoming geographic obstacles and having grades low enough to permit vehicle or foot travel,[43]: 15  and may be required to meet standards set by law[44] or official guidelines.[45] The process is often begun with the removal of earth and rock by digging or blasting, construction of embankments, bridges and tunnels, and removal of vegetation (this may involve deforestation) and followed by the laying of pavement material. A variety of road building equipment is employed in road building.[46][47]

After design, approval, planning, legal, and environmental considerations have been addressed alignment of the road is set out by a surveyor.[33] The radii and gradient are designed and staked out to best suit the natural ground levels and minimize the amount of cut and fill.[45]: 34  Great care is taken to preserve reference Benchmarks[45]: 59 

Roads are designed and built for primary use by vehicular and pedestrian traffic. Storm drainage and environmental considerations are a major concern. Erosion and sediment controls are constructed to prevent detrimental effects. Drainage lines are laid with sealed joints in the road easement with runoff coefficients and characteristics adequate for the land zoning and storm water system. Drainage systems must be capable of carrying the ultimate design flow from the upstream catchment with approval for the outfall from the appropriate authority to a watercourse, creek, river or the sea for drainage discharge.[45]: 38–40 

A borrow pit (source for obtaining fill, gravel, and rock) and a water source should be located near or in reasonable distance to the road construction site. Approval from local authorities may be required to draw water or for working (crushing and screening) of materials for construction needs. The topsoil and vegetation is removed from the borrow pit and stockpiled for subsequent rehabilitation of the extraction area. Side slopes in the excavation area not steeper than one vertical to two horizontal for safety reasons.[45]: 53–56 

Old road surfaces, fences, and buildings may need to be removed before construction can begin. Trees in the road construction area may be marked for retention. These protected trees should not have the topsoil within the area of the tree's drip line removed and the area should be kept clear of construction material and equipment. Compensation or replacement may be required if a protected tree is damaged. Much of the vegetation may be mulched and put aside for use during reinstatement. The topsoil is usually stripped and stockpiled nearby for rehabilitation of newly constructed embankments along the road. Stumps and roots are removed and holes filled as required before the earthwork begins. Final rehabilitation after road construction is completed will include seeding, planting, watering and other activities to reinstate the area to be consistent with the untouched surrounding areas.[45]: 66–67 

Processes during earthwork include excavation, removal of material to spoil, filling, compacting, construction and trimming. If rock or other unsuitable material is discovered it is removed, moisture content is managed and replaced with standard fill compacted to meet the design requirements (generally 90–95% relative compaction). Blasting is not frequently used to excavate the roadbed as the intact rock structure forms an ideal road base. When a depression must be filled to come up to the road grade the native bed is compacted after the topsoil has been removed. The fill is made by the "compacted layer method" where a layer of fill is spread then compacted to specifications, under saturated conditions. The process is repeated until the desired grade is reached.[45]: 68–69 

 
Typical pavement strata for a heavily traveled road

General fill material should be free of organics, meet minimum California bearing ratio (CBR) results and have a low plasticity index. The lower fill generally comprises sand or a sand-rich mixture with fine gravel, which acts as an inhibitor to the growth of plants or other vegetable matter. The compacted fill also serves as lower-stratum drainage. Select second fill (sieved) should be composed of gravel, decomposed rock or broken rock below a specified particle size and be free of large lumps of clay. Sand clay fill may also be used. The roadbed must be "proof rolled" after each layer of fill is compacted. If a roller passes over an area without creating visible deformation or spring the section is deemed to comply.[45]: 70–72 

Geosynthetics such as geotextiles, geogrids, and geocells are frequently used in the various pavement layers to improve road quality. These materials and methods are used in low-traffic private roadways as well as public roads and highways.[48] Geosynthetics perform four main functions in roads: separation, reinforcement, filtration, and drainage; which increase the pavement performance, reduce construction costs and decrease maintenance.[49][self-published source]

The completed roadway is finished by paving or left with a gravel or other natural surface. The type of road surface is dependent on economic factors and expected usage. Safety improvements such as traffic signs, crash barriers, raised pavement markers and other forms of road surface marking are installed.

According to a May 2009 report by the American Association of State Highway and Transportation Officials (AASHTO) and TRIP – a national transportation research organization – driving on rough roads costs the average American motorist approximately $400 a year in extra vehicle operating costs. Drivers living in urban areas with populations more than 250,000 are paying upwards of $750 more annually because of accelerated vehicle deterioration, increased maintenance, additional fuel consumption, and tire wear caused by poor road conditions.

When a single carriageway road is converted into dual carriageway by building a second separate carriageway alongside the first, it is usually referred to as duplication,[50] twinning or doubling. The original carriageway is changed from two-way to become one-way, while the new carriageway is one-way in the opposite direction. In the same way as converting railway lines from single track to double track, the new carriageway is not always constructed directly alongside the existing carriageway.

Reallocation

See also: Modal shift and Car-free movement

Roads that are intended for use by a particular mode of transport can be reallocated for another mode of transport,[51] i.e. by using traffic signs. For instance, in the ongoing road space reallocation effort, some roads (particularly in city centers) which are intended for use by cars are increasingly being repurposed for cycling and/or walking.[52][53][54]

Maintenance

See also: Roadworks and Road surface § Surface deterioration
 
"Road works ahead" sign, typically used in Europe

Like all structures, roads deteriorate over time. Deterioration is primarily due to environmental effects such as frost heaves, thermal cracking and oxidation often contribute, however accumulated damage from vehicles also contributes.[55] According to a series of experiments carried out in the late 1950s, called the AASHO Road Test, it was empirically determined that the effective damage done to the road is roughly proportional to the fourth power of axle weight.[56] A typical tractor-trailer weighing 80,000 pounds (36.287 t) with 8,000 pounds (3.629 t) on the steer axle and 36,000 pounds (16.329 t) on both of the tandem axle groups is expected to do 7,800 times more damage than a passenger vehicle with 2,000 pounds (0.907 t) on each axle. Potholes on roads are caused by rain damage and vehicle braking or related construction work.

 
Line marking in rural India

Pavements are designed for an expected service life or design life. In some parts of the United Kingdom the standard design life is 40 years for new bitumen and concrete pavement. Maintenance is considered in the whole life cost of the road with service at 10, 20 and 30 year milestones.[57] Roads can be and are designed for a variety of lives (8-, 15-, 30-, and 60-year designs). When pavement lasts longer than its intended life, it may have been overbuilt, and the original costs may have been too high. When a pavement fails before its intended design life, the owner may have excessive repair and rehabilitation costs. Some asphalt pavements are designed as perpetual pavements with an expected structural life in excess of 50 years.[58]

 
A white line used to designate a parking bay in Scotland. The line has deteriorated to the point that both an older yellow line and the underlying surface are visible beneath.

Many asphalt pavements built over 35 years ago, despite not being specifically designed as a perpetual pavement, have remained in good condition long past their design life.[59] Many concrete pavements built since the 1950s have significantly outlived their intended design lives.[60] Some roads like Chicago's Wacker Drive, a major two-level (and at one point, three-level) roadway in the downtown area, are being rebuilt with a designed service life of 100 years.[61]

Virtually all roads require some form of maintenance before they come to the end of their service life. Pro-active agencies use pavement management techniques to continually monitor road conditions and schedule preventive maintenance treatments as needed to prolong the lifespan of their roads. Technically advanced agencies monitor the road network surface condition with sophisticated equipment such as laser/inertial profilometers. These measurements include road curvature, cross slope, asperity, roughness, rutting and texture. Software algorithms use this data to recommend maintenance or new construction.

Maintenance treatments for asphalt concrete generally include thin asphalt overlays, crack sealing, surface rejuvenating, fog sealing, micro milling or diamond grinding and surface treatments. Thin surfacing preserves, protects and improves the functional condition of the road while reducing the need for routing maintenance, leading to extended service life without increasing structural capacity.[62]

Older concrete pavements that develop faults can be repaired with a dowel bar retrofit, in which slots are cut in the pavement at each joint, and dowel bars are placed in the slots, which are then filled with concrete patching material. This can extend the life of the concrete pavement for 15 years.[63]

Failure to maintain roads properly can create significant costs to society. A 2009 report released by the American Association of State Highway and Transportation Officials estimated that about 50% of the roads in the US are in bad condition, with urban areas worse. The report estimates that urban drivers pay an average of $746/year on vehicle repairs while the average US motorist pays about $335/year. In contrast, the average motorist pays about $171/year in road maintenance taxes (based on 600 gallons/year and $0.285/gallon tax).

Slab stabilization

Distress and serviceability loss on concrete roads can be caused by loss of support due to voids beneath the concrete pavement slabs. The voids usually occur near cracks or joints due to surface water infiltration. The most common causes of voids are pumping, consolidation, subgrade failure and bridge approach failure. Slab stabilization is a non-destructive method of solving this problem and is usually employed with other concrete pavement restoration methods including patching and diamond grinding. The technique restores support to concrete slabs by filing small voids that develop underneath the concrete slab at joints, cracks or the pavement edge.

The process consists of pumping a cementitious grout or polyurethane mixture through holes drilled through the slab. The grout can fill small voids beneath the slab and/or sub-base. The grout also displaces free water and helps keep water from saturating and weakening support under the joints and slab edge after stabilization is complete. The three steps for this method after finding the voids are locating and drilling holes, grout injection and post-testing the stabilized slabs.

Slab stabilization does not correct depressions, increase the design structural capacity, stop erosion or eliminate faulting. It does, however, restore the slab support, therefore, decreasing deflections under the load. Stabilization should only be performed at joints and cracks where the loss of support exists. Visual inspection is the simplest manner to find voids. Signs that repair is needed are transverse joint faulting, corner breaks and shoulder drop off and lines at or near joints and cracks. Deflection testing is another common procedure used to locate voids. It is recommended to do this testing at night as during cooler temperatures, joints open, aggregate interlock diminishes and load deflections are at their highest.

Testing

Ground penetrating radar pulses electromagnetic waves into the pavement and measures and graphically displays the reflected signal. This can reveal voids and other defects.

The epoxy/core test, detects voids by visual and mechanical methods. It consists of drilling a 25 to 50 millimeter hole through the pavement into the sub-base with a dry-bit roto-hammer. Next, a two-part epoxy is poured into the hole – dyed for visual clarity. Once the epoxy hardens, technicians drill through the hole. If a void is present, the epoxy will stick to the core and provide physical evidence.

Common stabilization materials include pozzolan-cement grout and polyurethane. The requirements for slab stabilization are strength and the ability to flow into or expand to fill small voids. Colloidal mixing equipment is necessary to use the pozzolan-cement grouts. The contractor must place the grout using a positive-displacement injection pump or a non-pulsing progressive cavity pump. A drill is also necessary but it must produce a clean hole with no surface spalling or breakouts. The injection devices must include a grout packer capable of sealing the hole. The injection device must also have a return hose or a fast-control reverse switch, in case workers detect slab movement on the uplift gauge. The uplift beam helps to monitor the slab deflection and has to have sensitive dial gauges.[64][65]

Joint sealing

Also called joint and crack repair, this method's purpose is to minimize infiltration of surface water and incompressible material into the joint system. Joint sealants are also used to reduce dowel bar corrosion in concrete pavement restoration techniques. Successful resealing consists of old sealant removal, shaping and cleaning the reservoir, installing the backer rod and installing the sealant. Sawing, manual removal, plowing and cutting are methods used to remove the old sealant. Saws are used to shape the reservoir. When cleaning the reservoir, no dust, dirt or traces of old sealant should remain. Thus, it is recommended to water wash, sand-blast and then air blow to remove any sand, dirt or dust. The backer rod installation requires a double-wheeled, steel roller to insert the rod to the desired depth. After inserting the backer rod, the sealant is placed into the joint. There are various materials to choose for this method including hot pour bituminous liquid, silicone and preformed compression seals.[64][66][67][68]

Safety considerations

See also: Road traffic safety

Careful design and construction of roads can increase road traffic safety and reduce the harm (deaths, injuries, and property damage) on the highway system from traffic collisions.

On neighborhood roads traffic calming, safety barriers, pedestrian crossings and cycle lanes can help protect pedestrians, cyclists, and drivers.

Lane markers in some countries and states are marked with Cat's eyes or Botts dots, (bright reflectors that do not fade like paint). Botts dots are not used where it is icy in the winter, because frost and snowplows can break the glue that holds them to the road, although they can be embedded in short, shallow trenches carved in the roadway, as is done in the mountainous regions of California.

For major roads risk can be reduced by providing limited access from properties and local roads, grade separated junctions and median dividers between opposite-direction traffic to reduce the likelihood of head-on collisions.

The placement of energy attenuation devices (e.g. guardrails, wide grassy areas, sand barrels) is also common. Some road fixtures such as road signs and fire hydrants are designed to collapse on impact. Light poles are designed to break at the base rather than violently stop a car that hits them. Highway authorities may also remove larger trees from the immediate vicinity of the road. During heavy rains, if the elevation of the road surface isn't higher than the surrounding landscape, it may result in flooding.[69]

Speed limits can improve road traffic safety and reduce the number of road traffic casualties from traffic collisions. In their World report on road traffic injury prevention report, the World Health Organization (WHO) identify speed control as one of various interventions likely to contribute to a reduction in road casualties.

Road conditions

 
Snow causing bad road conditions

Road conditions are the collection of factors describing the ease of driving on a particular stretch of road, or on the roads of a particular locality, including the quality of the pavement surface, potholes, road markings, and weather. It has been reported that "[p]roblems of transportation participants and road conditions are the main factors that lead to road traffic accidents".[70] It has further been specifically noted that "weather conditions and road conditions are interlinked as weather conditions affect the road conditions".[71] Specific aspects of road conditions can be of particular importance for particular purposes. For example, for autonomous vehicles such as self-driving cars, significant road conditions can include "shadowing and lighting changes, road surface texture changes, and road markings consisting of circular reflectors, dashed lines, and solid lines".[72]

Various government agencies and private entities, including local news services, track and report on road conditions to the public so that drivers going through a particular area can be aware of hazards that may exist in that area. News agencies, in turn, rely on tips from area residents with respect to certain aspects of road conditions in their coverage area.[73]

Environmental performance

Main article: Environmental impacts of roads
 
Air pollution along Pasadena Highway in Los Angeles
 
A dual carriageway section of National Highway 8 connecting Delhi to Gurgaon

Careful design and construction of a road can reduce any negative environmental impacts. Water management systems can be used to reduce the effect of pollutants from roads.[74][75] Rainwater and snowmelt running off of roads tends to pick up gasoline, motor oil, heavy metals, trash and other pollutants and result in water pollution. Road runoff is a major source of nickel, copper, zinc, cadmium, lead and polycyclic aromatic hydrocarbons (PAHs), which are created as combustion byproducts of gasoline and other fossil fuels.[76]

De-icing chemicals and sand can run off into roadsides, contaminate groundwater and pollute surface waters;[77] and road salts can be toxic to sensitive plants and animals.[78] Sand applied to icy roads can be ground up by traffic into fine particulates and contribute to air pollution.

Roads are a chief source of noise pollution. In the early 1970s, it was recognized[by whom?] that design of roads can be conducted to influence and minimize noise generation.[79] Noise barriers can reduce noise pollution near built-up areas. Regulations can restrict the use of engine braking.

Motor vehicle emissions contribute air pollution. Concentrations of air pollutants and adverse respiratory health effects are greater near the road than at some distance away from the road.[80] Road dust kicked up by vehicles may trigger allergic reactions.[81] In addition, on-road transportation greenhouse gas emissions are the largest single cause of climate change, scientists say.[82]

 
The A22(T) with line markings near Summer Hill, East Sussex, England
 
Road with guard rails in Kaluga Oblast, Russia
 
Road with traffic signs in the outskirts of Bern, Switzerland
 
NH 73 going to Bangalore
 
Ontario Highway 401, a route with a collector / express setup
 
The wide Coastal Road in the Philippines now called the Manila-Cavite Expressway

Regulation

 
Australian drive on left sign

Right- and left-hand traffic

Main article: Right- and left-hand traffic

Traffic flows on the right or on the left side of the road depending on the country.[83] In countries where traffic flows on the right, traffic signs are mostly on the right side of the road, roundabouts and traffic circles go counter-clockwise/anti-clockwise, and pedestrians crossing a two-way road should watch out for traffic from the left first.[84] In countries where traffic flows on the left, the reverse is true.

About 33% of the world by population drive on the left, and 67% keep right. By road distances, about 28% drive on the left, and 72% on the right,[85] even though originally most traffic drove on the left worldwide.[86]

Economics

Main article: Transport economics
 
A city street in Mumbai, India with left-hand traffic

Transport economics is used to understand both the relationship between the transport system and the wider economy and the complex network effects when there are multiple paths and competing modes for both personal and freight (road/rail/air/ferry) and where induced demand can result in increased on decreased transport levels when road provision is increased by building new roads or decreased (for example California State Route 480). Roads are generally built and maintained by the public sector using taxation although implementation may be through private contractors).[87][88] or occasionally using road tolls.[89]

Public-private partnerships are a way for communities to address the rising cost by injecting private funds into the infrastructure. There are four main ones:[90]

  • design/build
  • design/build/operate/maintain
  • design/build/finance/operate
  • build/own/operate

Society depends heavily on efficient roads. In the European Union (EU) 44% of all goods are moved by trucks over roads and 85% of all people are transported by cars, buses or coaches on roads.[91] The term was also commonly used to refer to roadsteads, waterways that lent themselves to use by shipping.

Construction costs

According to the New York State Thruway Authority,[92] some sample per-mile costs to construct multi-lane roads in several US northeastern states were:

Statistics

The United States has the largest network of roads of any country with 4,050,717 miles (6,518,997 km) as of 2009.[93] The Republic of India has the second-largest road system globally with 4,689,842 kilometres (2,914,133 mi) of road (2013).[94] The People's Republic of China is third with 3,583,715 kilometres (2,226,817 mi) of road (2007). The Federative Republic of Brazil has the fourth-largest road system in the world with 1,751,868 kilometres (1,088,560 mi) (2002). See List of countries by road network size. When looking only at expressways, the National Trunk Highway System (NTHS) in China has a total length of 45,000 kilometres (28,000 mi) at the end of 2006, and 60,300 km at the end of 2008, second only to the United States with 90,000 kilometres (56,000 mi) in 2005. However, as of 2017, China has 130,000 km of Expressways.[95][96]

Global connectivity

 
An ice road between the Hailuoto Island and the Mainland Finland at winter

Eurasia, Africa, North America, South America, and Australia each have an extensive road network that connects most cities. The North and South American road networks are separated by the Darién Gap, the only interruption in the Pan-American Highway. Eurasia and Africa are connected by roads on the Sinai Peninsula. The European Peninsula is connected to the Scandinavian Peninsula by the Øresund Bridge, and both have many connections to the mainland of Eurasia, including the bridges over the Bosphorus. Antarctica has very few roads and no continent-bridging network, though there are a few ice roads between bases, such as the South Pole Traverse. Bahrain is the only island country to be connected to a continental network by road (the King Fahd Causeway to Saudi Arabia).

Even well-connected road networks are controlled by many different legal jurisdictions, and laws such as which side of the road to drive on vary accordingly.

Many populated domestic islands are connected to the mainland by bridges. A very long example is the 113 mi (182 km) Overseas Highway connecting many of the Florida Keys with the continental United States.

Even on mainlands, some settlements have no roads connecting with the primary continental network, due to natural obstacles like mountains or wetlands, or high cost compared to the population served. Unpaved roads or lack of roads are more common in developing countries, and these can become impassible in wet conditions. As of 2014, only 43% of rural Africans have access to an all-season road.[97] Due to steepness, mud, snow, or fords, roads can sometimes be passable only to four-wheel drive vehicles, those with snow chains or snow tires, or those capable of deep wading or amphibious operation.

Most disconnected settlements have local road networks connecting ports, buildings, and other points of interest.

Where demand for travel by road vehicle to a disconnected island or mainland settlement is high, roll-on/roll-off ferries are commonly available if the journey is relatively short. For long-distance trips, passengers usually travel by air and rent a car upon arrival. If facilities are available, vehicles and cargo can also be shipped to many disconnected settlements by boat, or air transport at much greater expense. The island of Great Britain is connected to the European road network by Eurotunnel Shuttle – an example of a car shuttle train which is a service used in other parts of Europe to travel under mountains and over wetlands.

In polar areas, disconnected settlements are often more easily reached by snowmobile or dogsled in cold weather, which can produce sea ice that blocks ports, and bad weather that prevents flying. For example, resupply aircraft are only flown to Amundsen–Scott South Pole Station October to February, and many residents of coastal Alaska have bulk cargo shipped in only during the warmer months. Permanent darkness during the winter can also make long-distance travel more dangerous in polar areas. Continental road networks do reach into these areas, such as the Dalton Highway to the North Slope of Alaska, the R21 highway to Murmansk in Russia, and many roads in Scandinavia (though due to fjords water transport is sometimes faster). Large areas of Alaska, Canada, Greenland, and Siberia are sparsely connected. For example, all 25 communities of Nunavut are disconnected from each other and the main North American road network.[98]

Road transport of people and cargo by may also be obstructed by border controls and travel restrictions. For example, travel from other parts of Asia to South Korea would require passage through the hostile country of North Korea. Moving between most countries in Africa and Eurasia would require passing through Egypt and Israel, which is a politically sensitive area.

Some places are intentionally car-free, and roads (if present) might be used by bicycles or pedestrians.

Roads are under construction to many remote places, such as the villages of the Annapurna Circuit, and a road was completed in 2013 to Mêdog County. Additional intercontinental and transoceanic fixed links have been proposed, including a Bering Strait crossing that would connect Eurasia-Africa and North America, a Malacca Strait Bridge to the largest island of Indonesia from Asia, and a Strait of Gibraltar crossing to connect Europe and Africa directly.

See also

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January 21, 2023
road, other, uses, disambiguation, road, linear, conveyance, traffic, that, mostly, improved, surface, vehicles, motorized, motorized, pedestrians, unlike, streets, main, function, roads, transportation, there, many, types, roads, including, parkways, avenues,. For other uses see Road disambiguation A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles motorized and non motorized and pedestrians Unlike streets the main function of roads is transportation There are many types of roads including parkways avenues controlled access highways freeways motorways and expressways tollways interstates highways thoroughfares and local roads The primary features of roads include lanes sidewalks pavement roadways carriageways medians shoulders verges bike paths cycle paths and shared use paths Contents 1 Definitions 1 1 Australia 1 2 New Zealand 1 3 United Kingdom 1 4 United States 2 History 3 Design 4 Terminology 5 Construction 6 Reallocation 7 Maintenance 7 1 Slab stabilization 7 2 Testing 7 3 Joint sealing 8 Safety considerations 9 Road conditions 10 Environmental performance 11 Regulation 11 1 Right and left hand traffic 12 Economics 12 1 Construction costs 13 Statistics 14 Global connectivity 15 See also 16 ReferencesDefinitions Edit A bricked road in Bangladesh A gravel road in Namibia Historically many roads were simply recognizable routes without any formal construction or some maintenance 1 The Organization for Economic Co operation and Development OECD defines a road as a line of communication travelled way using a stabilized base other than rails or air strips open to public traffic primarily for the use of road motor vehicles running on their own wheels which includes bridges tunnels supporting structures junctions crossings interchanges and toll roads but not cycle paths 2 The Eurostat ITF and UNECE Glossary for Transport Statistics Illustrated defines a road as a Line of communication traveled way open to public traffic primarily for the use of road motor vehicles using a stabilized base other than rails or air strips Included are paved roads and other roads with a stabilized base e g gravel roads Roads also cover streets bridges tunnels supporting structures junctions crossings and interchanges Toll roads are also included Excluded are dedicated cycle lanes 3 The 1968 Vienna Convention on Road Traffic defines a road as the entire surface of any way or street open to public traffic 4 In urban areas roads may diverge through a city or village and be named as streets serving a dual function as urban space easement and route 5 Modern roads are normally smoothed paved or otherwise prepared to allow easy travel 6 Australia Edit See also Highways in Australia Part 2 Division 1 clauses 11 13 of the National Transport Commission Regulations 2006 defines a road in Australia as an area that is open to or used by the public and is developed for or has as one of its main uses the driving or riding of motor vehicles 7 Further it defines a shoulder typical an area of the road outside the edge line or the curb and a road related area which includes green areas separating roads areas designated for cyclists and areas generally accessible to the public for driving riding or parking vehicles New Zealand Edit In New Zealand the definition of a road is broad in common law 8 where the statutory definition includes areas the public has access to by right or not 9 Beaches publicly accessible car parks and yards even if privately owned river beds road shoulders verges wharves and bridges are included 10 However the definition of a road for insurance purposes may be restricted to reduce risk United Kingdom Edit In the United Kingdom The Highway Code details rules for road users but there is some ambiguity between the terms highway and road 11 For the purposes of the English law Highways Act 1980 which covers England and Wales but not Scotland or Northern Ireland road is any length of highway or of any other road to which the public has access and includes bridges over which a road passes 12 This includes footpaths bridleways and cycle tracks and also road and driveways on private land and many car parks 13 Vehicle Excise Duty a road use tax is payable on some vehicles used on the public road 13 The definition of a road depends on the definition of a highway there is no formal definition for a highway in the relevant Act A 1984 ruling said the land over which a public right of way exists is known as a highway and although most highways have been made up into roads and most easements of way exist over footpaths the presence or absence of a made road has nothing to do with the distinction 14 15 Another legal view is that while a highway historically included footpaths bridleways driftways etc it can now be used to mean those ways that allow the movement of motor vehicles and the term rights of way can be used to cover the wider usage 16 United States Edit In the United States laws distinguish between public roads which are open to public use 17 and private roads which are privately controlled 18 History EditMain article History of road transport Further information Gravel road and Trail Transfăgărășan called the best road in the world by Top Gear 19 The Porta Rosa a Greek street dating from the 3rd to 4th century BC in Velia with a paved surface and gutters A paved Roman road in Pompeii Old tractor road over farmland Ystad Sweden Ancient Sassanid Era Pathway in Behbahan Persia Ancient Cobblestoned Road in Behbahan The assertion that the first pathways were the trails made by animals has not been universally accepted in many cases animals do not follow constant paths 1 Some believe that some roads originated from following animal trails 20 21 The Icknield Way may exemplify this type of road origination where human and animal both selected the same natural line 22 By about 10 000 BC human travelers used rough roads pathways 1 The world s oldest known paved road was constructed in Egypt some time between 2600 and 2200 BC 23 Stone paved streets appear in the city of Ur in the Middle East dating back to 4000 BC 1 Corduroy roads log roads are found dating to 4000 BC in Glastonbury England 1 The Sweet Track a timber track causeway in England is one of the oldest engineered roads discovered and the oldest timber trackway discovered in Northern Europe Built in winter 3807 BC or spring 3806 BC tree ring dating dendrochronology enabled very precise dating It was claimed to be the oldest road in the world 24 25 until the 2009 discovery of a 6 000 year old trackway in Plumstead London 26 27 Brick paved streets appeared in India as early as 3000 BC 1 c 1995 BC an early subdividing of roadways evidenced with sidewalks built in Anatolia 28 In 500 BC Darius I the Great started an extensive road system for the Achaemenid Empire Persia including the Royal Road which was one of the finest highways of its time 29 connecting Sardis the westernmost major city of the empire to Susa The road remained in use after Roman times These road systems reached as far east as Bactria and India 30 In ancient times transport by river was far easier and faster than transport by road 25 especially considering the cost of road construction and the difference in carrying capacity between carts and river barges A hybrid of road transport and ship transport beginning in about 1740 is the horse drawn boat in which the horse follows a cleared path along the river bank 31 32 From about 312 BC the Roman Empire built straight 33 strong stone Roman roads throughout Europe and North Africa in support of its military campaigns At its peak the Roman Empire was connected by 29 major roads moving out from Rome and covering 78 000 kilometers or 52 964 Roman miles of paved roads 25 In the 8th century AD many roads were built throughout the Arab Empire The most sophisticated roads were those in Baghdad which were paved with tar Tar was derived from petroleum accessed from oil fields in the region through the chemical process of destructive distillation 34 The Highways Act 1555 in Britain transferred responsibility for maintaining roads from government to local parishes 25 This resulted in a poor and variable state of roads To remedy this the first of the turnpike trusts was established around 1706 to build good roads and collect tolls from passing vehicles Eventually there were approximately 1 100 trusts in Britain and some 36 800 km 22 870 miles of engineered roads 25 The Rebecca Riots in Carmarthenshire and Rhayader from 1839 to 1844 contributed to a Royal Commission that led to the demise of the system in 1844 35 which coincided with the development of the UK railway system In the late 19th century roading engineers began to cater for cyclists by building separate lanes alongside roadways From the beginning of the 20th century roads were increasingly built for tourism and also to create jobs A typical example of the stimulation of tourism is the Great Dolomite Road while the creation of the panoramic coastal road Strada Costiera between Duino and Barcola in 1928 was very much focused on creating jobs 36 37 Design Edit A highway in Tampere Finland Road design is part of highway engineering Structural road design is designing a road for the environment in order to extend its longevity and reduce maintenance The Shell pavement design method is used in many countries for the design of new asphalt roadsides Terminology EditMain article Glossary of road transport terms Adverse camber Where a road slopes towards the outside of a bend increasing the likelihood that vehicles travelling at speed will skid or topple Usually only a temporary situation during road maintenance Alignment The route of the road defined as a series of horizontal tangents and curves All weather road Unpaved road that is constructed of a material that does not create mud during rainfall Banked turn Belisha Beacon An orange globe lit at night used to highlight a pedestrian crossing Bicycle boulevard A street that allows local vehicle traffic but is prioritized for bicycles and other non motorized travel A beach road Newcastle NSW Australia Bollard Rigid posts that can be arranged in a line to close a road or path to vehicles above a certain width Byway Highway over which the public have a right to travel for vehicular and other kinds of traffic but is used mainly as a footpath or bridleway Bypass Road that avoids or bypasses a built up area town or village Bottleneck Section of a road with a carrying capacity substantially below that of other sections of the same road Botts dots Non reflective raised pavement marker used on roads Camber or crown The slope of the road surface downwards away from the centre of the road so that surface water can flow freely to the edge of the carriageway or on bends angling of the surface to lean traffic into the bend reducing the chance of a skid Cant Another name for cross slope or camber Carriageway Part of the road intended for the movement of road motor vehicles the parts of the road which form a shoulder for the lower or upper layers of the road surface are not part of the roadway nor are those parts of the road intended for the circulation of road vehicles which are not self propelled or for the parking of vehicles 3 Cat s eye Reflective raised pavement marker used on roads Chicane Sequence of tight serpentine curves usually an S shape curve or a bus stop Chipseal Road surface composed of a thin layer of crushed stone chips and asphalt emulsion It seals the surface and protects it from weather but provides no structural strength It is cheaper than asphalt concrete or concrete In the United States it is usually only used on low volume rural roads Corniche Road on the side of a cliff or mountain with the ground rising on one side and falling away on the other Cross slope The slope of the pavement expressed as units of rise per unit of run or as a percentage Curb kerb A raised edge at the side of the roadway Curb extension also kerb extension bulb out nib elephant ear curb bulge and blister Traffic calming measure intended to slow the speed of traffic and increase driver awareness particularly in built up and residential neighborhoods Cycle lane Part of a carriageway designated for cycles and distinguished from the rest of the carriageway by longitudinal road markings Mopeds may also be allowed to use a cycle lane 3 Cycle track Independent road or part of a road designated for cycles and sign posted as such A cycle track is separated from other roads or other parts of the same road by structural means Mopeds may also be allowed to use the cycle track 3 Cycling infrastructure Cycling friendly infrastructure integrated into the roadway or in its own right of way Drainage gradient Farm to market road A state road or county road that connects rural or agricultural areas to market towns Fork literally fork in the road Type of intersection where a road splits Grade Longitudinal slope Green lane UK Unsurfaced road may be so infrequently used that vegetation colonises freely hence green Many green lanes are ancient routes that have existed for millennia Guide rail Prevents vehicles from veering off the road into oncoming traffic crashing against solid objects or falling from a road Also called a guard rail or traffic barrier Gutter A drainage channel usually at the edge of the road or along a median Interstate Highway System United States System of Interstate and Defense Highways Lane One of the longitudinal strips into which a carriageway is divisible whether or not defined by longitudinal road markings which is wide enough for one moving line of motor vehicles other than motorcycles 3 Layby Pullout pull off A paved area beside a main road where cars can stop temporarily to let another car pass Loose chippings The hazard of stone chippings that have come loose Median On dual carriageway roads including controlled access highways divided highways and many limited access roads the central reservation British English median North American English median strip North American English and Australian English neutral ground Louisiana English or central nature strip Australian English Area that separates opposing lanes of traffic Motorway Europe Freeways in the US Special road in the UK Road specially designed and built for motor traffic which does not serve properties bordering on it with separate carriageways for traffic in two directions with no crossings at the same level road railway tramway track or footpath and sign posted as a motorway and is reserved for specific categories of road motor vehicles 3 Mountain pass A relatively low level route through a range of mountains Milestone One of a series of numbered markers placed along a road often at regular intervals showing the distance to destinations National Highway Road built and maintained by a national authority Pavement The road regarded as a geoconstruction In the UK the term is road surface and the pavement is a pedestrian walkway alongside the road Pedestrian crossing Designated point on a road where road marking or other means helps pedestrians cross safely Pelican crossing officially Pelicon crossing UK A PEdestrian LIght CONtrolled crossing Private highway Highway owned and operated for profit by private industry Private road Road owned and maintained by a private individual organization or company rather than by a government Profile The vertical alignment of a road expressed as a series of grades connected by parabolic curves Protected Intersections for Bicycles A much safer design with a corner refuge island a setback crossing of the pedestrians and cyclists generally between 1 5 7 metres of setback a forward stop bar which allows cyclists to stop for a traffic light well ahead of motor traffic who must stop behind the crosswalk Separate signal staging or at least an advance green for cyclists and pedestrians is used to give cyclists and pedestrians no conflicts or a head start over traffic The design makes a right turn on red and sometimes left on red depending on the geometry of the intersection in question possible in many cases often without stopping 38 Protected Bicycle Path Cyclists ideally have a protected bike lane on separated by a concrete median with splay kerbs if possible and have a protected bike lane width of at least 2 metres if possible one way In the Netherlands most one way cycle paths are at least 2 5 metres wide 39 Public space Place where anyone has a right to come without being excluded because of economic or social conditions Ranch road U S road that connects rural and agricultural areas to market towns Road number Often assigned to identify a stretch of public roads often dependent on the type of road with numbers differentiating between interstates motorways arterial thoroughfares etc Road traffic safety Process to reduce the harm deaths injuries and property damage that result from vehicle crashes on public roads Roadworks Part or all of the road is occupied for work or maintenance Roughness Deviations from a true planar pavement surface which affects vehicle suspension deflection dynamic loading ride quality surface drainage and winter operations Roughness have wavelengths ranging from 500 mm up to some 40 m The upper limit may be as high as 350 m when considering motion sickness aspects motion sickness is generated by motion with down to 0 1 Hz frequency in an ambulance car driving 78 mph 126 km h waves with up to 350 m will excite motion sickness Roundabout A road junction where typically three or more roads are joined by a circular section of road Traffic on the roundabout has priority over traffic on approach roads unless indicated otherwise In countries where traffic drives on the left the roundabout is traveled in a clockwise direction Also known as an island in parts of the UK Segregated Bicycle Path Cyclists ideally have a protected bike lane separated by a concrete median with splay kerbs if possible and have a protected bike lane width of at least 2 meters if possible one way In the Netherlands most one way cycle paths are at least 2 5 metres wide 39 Shoulder also hard shoulder A clear level area to the side of the roadway available for stopping if needed State highway Road numbered by the state falling below numbered national highways like U S Routes in the hierarchy or a road maintained by the state including nationally numbered highways Traffic Pedestrians ridden or herded animals vehicles bicycles and other conveyances using any road for purposes of travel 40 Texture roads Deviations from a true planar pavement surface which affects the interaction between road and tire Microtexture have wavelengths below 0 5 mm Macrotexture below 50 mm and Megatexture below 500 mm Traffic calming Set of strategies used by urban planners and traffic engineers to slow down or reduce motor vehicle traffic thereby improving safety for pedestrians and bicyclists and improving the environment for residents Traffic island UK A small raised area used to help define the traffic flow which may also act as a refuge for pedestrians crossing the carriageway or a location for signs barriers or lights a synonym for roundabout in some parts of the UK Traffic light Also known as a traffic signal stop light stop and go lights a signaling device at a road intersection pedestrian crossing or other location that assigns right of way to different approaches to an intersection Zebra crossing UK A pedestrian crossing marked by black and white stripes on the carriagewayConstruction EditSee also Roadworks Macadam and Track bed Layers in the construction of a mortarless pavement A Subgrade B Subbase C Base course D Paver base E Pavers F Fine grained sand In transport engineering subgrade is the native material underneath a constructed road File Burbank Ave I 5 overpass under construction in Burbank California JPG thumb Overpass under construction over Interstate 5 in Burbank California USA 41 42 File us land survey officer jpg thumb Surveyor at work with a leveling instrument Asphalt layer and Hamm road roller Sub base layer composed of cement based material being applied during construction of the M8 motorway in Ireland Road construction in Myanmar Clearing rocks from mountain road in Spiti Road construction requires the creation of an engineered continuous right of way or roadbed overcoming geographic obstacles and having grades low enough to permit vehicle or foot travel 43 15 and may be required to meet standards set by law 44 or official guidelines 45 The process is often begun with the removal of earth and rock by digging or blasting construction of embankments bridges and tunnels and removal of vegetation this may involve deforestation and followed by the laying of pavement material A variety of road building equipment is employed in road building 46 47 After design approval planning legal and environmental considerations have been addressed alignment of the road is set out by a surveyor 33 The radii and gradient are designed and staked out to best suit the natural ground levels and minimize the amount of cut and fill 45 34 Great care is taken to preserve reference Benchmarks 45 59 Roads are designed and built for primary use by vehicular and pedestrian traffic Storm drainage and environmental considerations are a major concern Erosion and sediment controls are constructed to prevent detrimental effects Drainage lines are laid with sealed joints in the road easement with runoff coefficients and characteristics adequate for the land zoning and storm water system Drainage systems must be capable of carrying the ultimate design flow from the upstream catchment with approval for the outfall from the appropriate authority to a watercourse creek river or the sea for drainage discharge 45 38 40 A borrow pit source for obtaining fill gravel and rock and a water source should be located near or in reasonable distance to the road construction site Approval from local authorities may be required to draw water or for working crushing and screening of materials for construction needs The topsoil and vegetation is removed from the borrow pit and stockpiled for subsequent rehabilitation of the extraction area Side slopes in the excavation area not steeper than one vertical to two horizontal for safety reasons 45 53 56 Old road surfaces fences and buildings may need to be removed before construction can begin Trees in the road construction area may be marked for retention These protected trees should not have the topsoil within the area of the tree s drip line removed and the area should be kept clear of construction material and equipment Compensation or replacement may be required if a protected tree is damaged Much of the vegetation may be mulched and put aside for use during reinstatement The topsoil is usually stripped and stockpiled nearby for rehabilitation of newly constructed embankments along the road Stumps and roots are removed and holes filled as required before the earthwork begins Final rehabilitation after road construction is completed will include seeding planting watering and other activities to reinstate the area to be consistent with the untouched surrounding areas 45 66 67 Processes during earthwork include excavation removal of material to spoil filling compacting construction and trimming If rock or other unsuitable material is discovered it is removed moisture content is managed and replaced with standard fill compacted to meet the design requirements generally 90 95 relative compaction Blasting is not frequently used to excavate the roadbed as the intact rock structure forms an ideal road base When a depression must be filled to come up to the road grade the native bed is compacted after the topsoil has been removed The fill is made by the compacted layer method where a layer of fill is spread then compacted to specifications under saturated conditions The process is repeated until the desired grade is reached 45 68 69 Typical pavement strata for a heavily traveled road General fill material should be free of organics meet minimum California bearing ratio CBR results and have a low plasticity index The lower fill generally comprises sand or a sand rich mixture with fine gravel which acts as an inhibitor to the growth of plants or other vegetable matter The compacted fill also serves as lower stratum drainage Select second fill sieved should be composed of gravel decomposed rock or broken rock below a specified particle size and be free of large lumps of clay Sand clay fill may also be used The roadbed must be proof rolled after each layer of fill is compacted If a roller passes over an area without creating visible deformation or spring the section is deemed to comply 45 70 72 Geosynthetics such as geotextiles geogrids and geocells are frequently used in the various pavement layers to improve road quality These materials and methods are used in low traffic private roadways as well as public roads and highways 48 Geosynthetics perform four main functions in roads separation reinforcement filtration and drainage which increase the pavement performance reduce construction costs and decrease maintenance 49 self published source The completed roadway is finished by paving or left with a gravel or other natural surface The type of road surface is dependent on economic factors and expected usage Safety improvements such as traffic signs crash barriers raised pavement markers and other forms of road surface marking are installed According to a May 2009 report by the American Association of State Highway and Transportation Officials AASHTO and TRIP a national transportation research organization driving on rough roads costs the average American motorist approximately 400 a year in extra vehicle operating costs Drivers living in urban areas with populations more than 250 000 are paying upwards of 750 more annually because of accelerated vehicle deterioration increased maintenance additional fuel consumption and tire wear caused by poor road conditions When a single carriageway road is converted into dual carriageway by building a second separate carriageway alongside the first it is usually referred to as duplication 50 twinning or doubling The original carriageway is changed from two way to become one way while the new carriageway is one way in the opposite direction In the same way as converting railway lines from single track to double track the new carriageway is not always constructed directly alongside the existing carriageway Reallocation EditSee also Modal shift and Car free movement Roads that are intended for use by a particular mode of transport can be reallocated for another mode of transport 51 i e by using traffic signs For instance in the ongoing road space reallocation effort some roads particularly in city centers which are intended for use by cars are increasingly being repurposed for cycling and or walking 52 53 54 Maintenance EditSee also Roadworks and Road surface Surface deterioration Road works ahead sign typically used in Europe Like all structures roads deteriorate over time Deterioration is primarily due to environmental effects such as frost heaves thermal cracking and oxidation often contribute however accumulated damage from vehicles also contributes 55 According to a series of experiments carried out in the late 1950s called the AASHO Road Test it was empirically determined that the effective damage done to the road is roughly proportional to the fourth power of axle weight 56 A typical tractor trailer weighing 80 000 pounds 36 287 t with 8 000 pounds 3 629 t on the steer axle and 36 000 pounds 16 329 t on both of the tandem axle groups is expected to do 7 800 times more damage than a passenger vehicle with 2 000 pounds 0 907 t on each axle Potholes on roads are caused by rain damage and vehicle braking or related construction work Line marking in rural India Pavements are designed for an expected service life or design life In some parts of the United Kingdom the standard design life is 40 years for new bitumen and concrete pavement Maintenance is considered in the whole life cost of the road with service at 10 20 and 30 year milestones 57 Roads can be and are designed for a variety of lives 8 15 30 and 60 year designs When pavement lasts longer than its intended life it may have been overbuilt and the original costs may have been too high When a pavement fails before its intended design life the owner may have excessive repair and rehabilitation costs Some asphalt pavements are designed as perpetual pavements with an expected structural life in excess of 50 years 58 A white line used to designate a parking bay in Scotland The line has deteriorated to the point that both an older yellow line and the underlying surface are visible beneath Many asphalt pavements built over 35 years ago despite not being specifically designed as a perpetual pavement have remained in good condition long past their design life 59 Many concrete pavements built since the 1950s have significantly outlived their intended design lives 60 Some roads like Chicago s Wacker Drive a major two level and at one point three level roadway in the downtown area are being rebuilt with a designed service life of 100 years 61 Virtually all roads require some form of maintenance before they come to the end of their service life Pro active agencies use pavement management techniques to continually monitor road conditions and schedule preventive maintenance treatments as needed to prolong the lifespan of their roads Technically advanced agencies monitor the road network surface condition with sophisticated equipment such as laser inertial profilometers These measurements include road curvature cross slope asperity roughness rutting and texture Software algorithms use this data to recommend maintenance or new construction Maintenance treatments for asphalt concrete generally include thin asphalt overlays crack sealing surface rejuvenating fog sealing micro milling or diamond grinding and surface treatments Thin surfacing preserves protects and improves the functional condition of the road while reducing the need for routing maintenance leading to extended service life without increasing structural capacity 62 Older concrete pavements that develop faults can be repaired with a dowel bar retrofit in which slots are cut in the pavement at each joint and dowel bars are placed in the slots which are then filled with concrete patching material This can extend the life of the concrete pavement for 15 years 63 Failure to maintain roads properly can create significant costs to society A 2009 report released by the American Association of State Highway and Transportation Officials estimated that about 50 of the roads in the US are in bad condition with urban areas worse The report estimates that urban drivers pay an average of 746 year on vehicle repairs while the average US motorist pays about 335 year In contrast the average motorist pays about 171 year in road maintenance taxes based on 600 gallons year and 0 285 gallon tax Slab stabilization Edit Distress and serviceability loss on concrete roads can be caused by loss of support due to voids beneath the concrete pavement slabs The voids usually occur near cracks or joints due to surface water infiltration The most common causes of voids are pumping consolidation subgrade failure and bridge approach failure Slab stabilization is a non destructive method of solving this problem and is usually employed with other concrete pavement restoration methods including patching and diamond grinding The technique restores support to concrete slabs by filing small voids that develop underneath the concrete slab at joints cracks or the pavement edge The process consists of pumping a cementitious grout or polyurethane mixture through holes drilled through the slab The grout can fill small voids beneath the slab and or sub base The grout also displaces free water and helps keep water from saturating and weakening support under the joints and slab edge after stabilization is complete The three steps for this method after finding the voids are locating and drilling holes grout injection and post testing the stabilized slabs Slab stabilization does not correct depressions increase the design structural capacity stop erosion or eliminate faulting It does however restore the slab support therefore decreasing deflections under the load Stabilization should only be performed at joints and cracks where the loss of support exists Visual inspection is the simplest manner to find voids Signs that repair is needed are transverse joint faulting corner breaks and shoulder drop off and lines at or near joints and cracks Deflection testing is another common procedure used to locate voids It is recommended to do this testing at night as during cooler temperatures joints open aggregate interlock diminishes and load deflections are at their highest Testing Edit Ground penetrating radar pulses electromagnetic waves into the pavement and measures and graphically displays the reflected signal This can reveal voids and other defects The epoxy core test detects voids by visual and mechanical methods It consists of drilling a 25 to 50 millimeter hole through the pavement into the sub base with a dry bit roto hammer Next a two part epoxy is poured into the hole dyed for visual clarity Once the epoxy hardens technicians drill through the hole If a void is present the epoxy will stick to the core and provide physical evidence Common stabilization materials include pozzolan cement grout and polyurethane The requirements for slab stabilization are strength and the ability to flow into or expand to fill small voids Colloidal mixing equipment is necessary to use the pozzolan cement grouts The contractor must place the grout using a positive displacement injection pump or a non pulsing progressive cavity pump A drill is also necessary but it must produce a clean hole with no surface spalling or breakouts The injection devices must include a grout packer capable of sealing the hole The injection device must also have a return hose or a fast control reverse switch in case workers detect slab movement on the uplift gauge The uplift beam helps to monitor the slab deflection and has to have sensitive dial gauges 64 65 Joint sealing Edit Also called joint and crack repair this method s purpose is to minimize infiltration of surface water and incompressible material into the joint system Joint sealants are also used to reduce dowel bar corrosion in concrete pavement restoration techniques Successful resealing consists of old sealant removal shaping and cleaning the reservoir installing the backer rod and installing the sealant Sawing manual removal plowing and cutting are methods used to remove the old sealant Saws are used to shape the reservoir When cleaning the reservoir no dust dirt or traces of old sealant should remain Thus it is recommended to water wash sand blast and then air blow to remove any sand dirt or dust The backer rod installation requires a double wheeled steel roller to insert the rod to the desired depth After inserting the backer rod the sealant is placed into the joint There are various materials to choose for this method including hot pour bituminous liquid silicone and preformed compression seals 64 66 67 68 Safety considerations Edit Pedestrian crossing line markings and street furniture See also Road traffic safety Careful design and construction of roads can increase road traffic safety and reduce the harm deaths injuries and property damage on the highway system from traffic collisions On neighborhood roads traffic calming safety barriers pedestrian crossings and cycle lanes can help protect pedestrians cyclists and drivers Lane markers in some countries and states are marked with Cat s eyes or Botts dots bright reflectors that do not fade like paint Botts dots are not used where it is icy in the winter because frost and snowplows can break the glue that holds them to the road although they can be embedded in short shallow trenches carved in the roadway as is done in the mountainous regions of California For major roads risk can be reduced by providing limited access from properties and local roads grade separated junctions and median dividers between opposite direction traffic to reduce the likelihood of head on collisions The placement of energy attenuation devices e g guardrails wide grassy areas sand barrels is also common Some road fixtures such as road signs and fire hydrants are designed to collapse on impact Light poles are designed to break at the base rather than violently stop a car that hits them Highway authorities may also remove larger trees from the immediate vicinity of the road During heavy rains if the elevation of the road surface isn t higher than the surrounding landscape it may result in flooding 69 Speed limits can improve road traffic safety and reduce the number of road traffic casualties from traffic collisions In their World report on road traffic injury prevention report the World Health Organization WHO identify speed control as one of various interventions likely to contribute to a reduction in road casualties Road conditions Edit Snow causing bad road conditions Road conditions are the collection of factors describing the ease of driving on a particular stretch of road or on the roads of a particular locality including the quality of the pavement surface potholes road markings and weather It has been reported that p roblems of transportation participants and road conditions are the main factors that lead to road traffic accidents 70 It has further been specifically noted that weather conditions and road conditions are interlinked as weather conditions affect the road conditions 71 Specific aspects of road conditions can be of particular importance for particular purposes For example for autonomous vehicles such as self driving cars significant road conditions can include shadowing and lighting changes road surface texture changes and road markings consisting of circular reflectors dashed lines and solid lines 72 Various government agencies and private entities including local news services track and report on road conditions to the public so that drivers going through a particular area can be aware of hazards that may exist in that area News agencies in turn rely on tips from area residents with respect to certain aspects of road conditions in their coverage area 73 Environmental performance EditMain article Environmental impacts of roads Air pollution along Pasadena Highway in Los Angeles A dual carriageway section of National Highway 8 connecting Delhi to Gurgaon Careful design and construction of a road can reduce any negative environmental impacts Water management systems can be used to reduce the effect of pollutants from roads 74 75 Rainwater and snowmelt running off of roads tends to pick up gasoline motor oil heavy metals trash and other pollutants and result in water pollution Road runoff is a major source of nickel copper zinc cadmium lead and polycyclic aromatic hydrocarbons PAHs which are created as combustion byproducts of gasoline and other fossil fuels 76 De icing chemicals and sand can run off into roadsides contaminate groundwater and pollute surface waters 77 and road salts can be toxic to sensitive plants and animals 78 Sand applied to icy roads can be ground up by traffic into fine particulates and contribute to air pollution Roads are a chief source of noise pollution In the early 1970s it was recognized by whom that design of roads can be conducted to influence and minimize noise generation 79 Noise barriers can reduce noise pollution near built up areas Regulations can restrict the use of engine braking Motor vehicle emissions contribute air pollution Concentrations of air pollutants and adverse respiratory health effects are greater near the road than at some distance away from the road 80 Road dust kicked up by vehicles may trigger allergic reactions 81 In addition on road transportation greenhouse gas emissions are the largest single cause of climate change scientists say 82 The A22 T with line markings near Summer Hill East Sussex England Road with guard rails in Kaluga Oblast Russia Road with traffic signs in the outskirts of Bern Switzerland NH 73 going to Bangalore Ontario Highway 401 a route with a collector express setup The wide Coastal Road in the Philippines now called the Manila Cavite ExpresswayRegulation Edit Australian drive on left sign Right and left hand traffic Edit Main article Right and left hand traffic Traffic flows on the right or on the left side of the road depending on the country 83 In countries where traffic flows on the right traffic signs are mostly on the right side of the road roundabouts and traffic circles go counter clockwise anti clockwise and pedestrians crossing a two way road should watch out for traffic from the left first 84 In countries where traffic flows on the left the reverse is true About 33 of the world by population drive on the left and 67 keep right By road distances about 28 drive on the left and 72 on the right 85 even though originally most traffic drove on the left worldwide 86 Economics EditMain article Transport economics A city street in Mumbai India with left hand traffic Transport economics is used to understand both the relationship between the transport system and the wider economy and the complex network effects when there are multiple paths and competing modes for both personal and freight road rail air ferry and where induced demand can result in increased on decreased transport levels when road provision is increased by building new roads or decreased for example California State Route 480 Roads are generally built and maintained by the public sector using taxation although implementation may be through private contractors 87 88 or occasionally using road tolls 89 Public private partnerships are a way for communities to address the rising cost by injecting private funds into the infrastructure There are four main ones 90 design build design build operate maintain design build finance operate build own operateSociety depends heavily on efficient roads In the European Union EU 44 of all goods are moved by trucks over roads and 85 of all people are transported by cars buses or coaches on roads 91 The term was also commonly used to refer to roadsteads waterways that lent themselves to use by shipping Construction costs Edit According to the New York State Thruway Authority 92 some sample per mile costs to construct multi lane roads in several US northeastern states were Connecticut Turnpike 3 449 000 per mile New Jersey Turnpike 2 200 000 per mile Pennsylvania Turnpike Delaware Extension 1 970 000 per mile Northern Indiana Toll Road 1 790 000 per mile Garden State Parkway 1 720 000 per mile Massachusetts Turnpike 1 600 000 per mile Thruway New York to Pennsylvania Line 1 547 000 per mile Ohio Turnpike 1 352 000 per mile Pennsylvania Turnpike early construction 736 000 per mileStatistics EditThe United States has the largest network of roads of any country with 4 050 717 miles 6 518 997 km as of 2009 93 The Republic of India has the second largest road system globally with 4 689 842 kilometres 2 914 133 mi of road 2013 94 The People s Republic of China is third with 3 583 715 kilometres 2 226 817 mi of road 2007 The Federative Republic of Brazil has the fourth largest road system in the world with 1 751 868 kilometres 1 088 560 mi 2002 See List of countries by road network size When looking only at expressways the National Trunk Highway System NTHS in China has a total length of 45 000 kilometres 28 000 mi at the end of 2006 and 60 300 km at the end of 2008 second only to the United States with 90 000 kilometres 56 000 mi in 2005 However as of 2017 China has 130 000 km of Expressways 95 96 Global connectivity Edit An ice road between the Hailuoto Island and the Mainland Finland at winter Eurasia Africa North America South America and Australia each have an extensive road network that connects most cities The North and South American road networks are separated by the Darien Gap the only interruption in the Pan American Highway Eurasia and Africa are connected by roads on the Sinai Peninsula The European Peninsula is connected to the Scandinavian Peninsula by the Oresund Bridge and both have many connections to the mainland of Eurasia including the bridges over the Bosphorus Antarctica has very few roads and no continent bridging network though there are a few ice roads between bases such as the South Pole Traverse Bahrain is the only island country to be connected to a continental network by road the King Fahd Causeway to Saudi Arabia Even well connected road networks are controlled by many different legal jurisdictions and laws such as which side of the road to drive on vary accordingly Many populated domestic islands are connected to the mainland by bridges A very long example is the 113 mi 182 km Overseas Highway connecting many of the Florida Keys with the continental United States Even on mainlands some settlements have no roads connecting with the primary continental network due to natural obstacles like mountains or wetlands or high cost compared to the population served Unpaved roads or lack of roads are more common in developing countries and these can become impassible in wet conditions As of 2014 only 43 of rural Africans have access to an all season road 97 Due to steepness mud snow or fords roads can sometimes be passable only to four wheel drive vehicles those with snow chains or snow tires or those capable of deep wading or amphibious operation Most disconnected settlements have local road networks connecting ports buildings and other points of interest Where demand for travel by road vehicle to a disconnected island or mainland settlement is high roll on roll off ferries are commonly available if the journey is relatively short For long distance trips passengers usually travel by air and rent a car upon arrival If facilities are available vehicles and cargo can also be shipped to many disconnected settlements by boat or air transport at much greater expense The island of Great Britain is connected to the European road network by Eurotunnel Shuttle an example of a car shuttle train which is a service used in other parts of Europe to travel under mountains and over wetlands In polar areas disconnected settlements are often more easily reached by snowmobile or dogsled in cold weather which can produce sea ice that blocks ports and bad weather that prevents flying For example resupply aircraft are only flown to Amundsen Scott South Pole Station October to February and many residents of coastal Alaska have bulk cargo shipped in only during the warmer months Permanent darkness during the winter can also make long distance travel more dangerous in polar areas Continental road networks do reach into these areas such as the Dalton Highway to the North Slope of Alaska the R21 highway to Murmansk in Russia and many roads in Scandinavia though due to fjords water transport is sometimes faster Large areas of Alaska Canada Greenland and Siberia are sparsely connected For example all 25 communities of Nunavut are disconnected from each other and the main North American road network 98 Road transport of people and cargo by may also be obstructed by border controls and travel restrictions For example travel from other parts of Asia to South Korea would require passage through the hostile country of North Korea Moving between most countries in Africa and Eurasia would require passing through Egypt and Israel which is a politically sensitive area Some places are intentionally car free and roads if present might be used by bicycles or pedestrians Roads are under construction to many remote places such as the villages of the Annapurna Circuit and a road was completed in 2013 to Medog County Additional intercontinental and transoceanic fixed links have been proposed including a Bering Strait crossing that would connect Eurasia Africa and North America a Malacca Strait Bridge to the largest island of Indonesia from Asia and a Strait of Gibraltar crossing to connect Europe and Africa directly See also Edit Roads portalEmbankment transportation Gravel road Highway engineering Intersection road Issue tracking systems for reporting road defects List of countries by road network size List of roads and highways Pedestrian zone Road expansion Road slipperiness Road transport Track bed Trade routeReferences Edit a b c d e f Lay Maxwell G 1992 Ways of the World A History of the World s Roads and of the Vehicles that Used Them Rutgers University Press ISBN 978 0 8135 2691 1 Ways of the world Rutgers University Press New Brunswick Glossary of Statistical Terms OECD 2004 02 26 Retrieved 2007 07 17 a b c d e f Illustrated Glossary for Transport Statistics PDF International Transport Forum Retrieved 2019 09 27 Road Traffic Convention 1968 PDF unece org Retrieved 2019 09 27 What is the difference between a road and a street Word FAQ Dictionary com Lexico Publishing Group LLC 2007 Retrieved 2007 03 24 Road Infrastructure Strategic Framework for South Africa A Discussion Document National Department of Transport South Africa Archived from the original on 2007 09 27 Retrieved 2007 03 24 Infrastructure National Transport Commission Road Transport Legislation Australian Road Rules Regulations 2006 legislation gov au Retrieved 2019 12 16 Land Transport Act 1998 No 110 as at 29 October 2019 Public Act Contents New Zealand Legislation legislation govt nz Retrieved 2019 12 16 What Is a road NZ Transport Agency nzta govt nz Retrieved 2019 12 16 What is the legal definition of a road drivingtests co nz Retrieved 2019 12 16 Annex 4 The road user and the law The Highway Code Guidance GOV UK www gov uk Road Traffic Regulation Act 1984 142 General interpretation of Act Legislation road a in England and Wales means any length of highway or of any other road to which the public has access and includes bridges over which a road passes and b in Scotland has the same meaning as in the Roads Scotland Act 1984 a b The road user and the law Most of the provisions apply on all roads throughout Great Britain although there are some exceptions Reference listed says 1984 This description is used in several rules going back to at least 1975 The law of real property Stevens 1975 Authors Robert Megarry Sir Robert Edgar Megarry Sir William Wade Judgment Director of Public Prosecutions v Jones and Another On Appeal from a Divisional Court of the Queen s Bench Division Archived from the original on 2010 04 03 The land over which a public right of way exists is known as a highway and although most highways have been made up into roads and most easements of way exist over footpaths the presence or absence of a made road has nothing to do with the distinction There may be a highway over a footpath while a well made road may be subject only to an easement of way or may exist only for the landowner s benefit and be subject to no easement at all Local government law Highway law Historically a highway comprehended any path in which members of the public had the right to pass and re pass without let or hindrance The term embraced footpaths bridleways driftways and so forth The advent of the motor vehicle and its peculiar requirements has seen increasing distinctions between paths over which walkers and riders have a right of way and those ways that are predominantly used by motor vehicles The former may be usefully termed rights of way and are the subject of a separate entry in this web and the latter may be termed highways Leonard M Brent April 2017 The Public Nature of Indian Reservation Roads American Indian Law Journal 1 40 Retrieved 8 November 2021 Levinson David 2006 Street smart competition entrepreneurship and the future of roads New Brunswick N J Transaction Publishers p 80 ISBN 9781315130330 Top gear BBC 2010 Archived from the original on 2021 10 30 Retrieved 2010 09 08 Helbing D Molnar P Farkas I J Bolay K 2001 Environment and Planning B Planning and Design 2001 volume 28 Self organizing pedestrian movement PDF Environment and Planning B Planning and Design 28 3 376 doi 10 1068 b2697 S2CID 16276539 Marshalls Heath Nature Reserve History wheathampstead net 24 February 2003 Retrieved 2007 04 28 The Icknield Way Path Icknield Way Association 2004 Retrieved 2007 04 29 John Noble Wildord 1994 05 08 World s Oldest Paved Road Found in Egypt The New York Times Retrieved 2012 02 11 The Somerset Levels the oldest timber trackway discovered in Northern Europe Current Archaeology 172 Current Archaeology February 2001 Archived from the original on 2007 03 11 Retrieved 2007 03 25 a b c d e O Flaherty Coleman A 2002 Highways The Location Design Construction amp Maintenance of Road Pavements Elsevier ISBN 978 0 7506 5090 8 Oldest Trackway found in Plumstead Archaeology about com 2009 08 15 Retrieved 2013 08 14 London s earliest timber structure found during Belmarsh prison dig Eurekalert org 2009 08 12 Retrieved 2013 08 14 Anastasia Loukaitou Sideris Renia Ehrenfeucht 2009 Sidewalks Conflict and Negotiation Over Public Space MIT Press p 15 ISBN 978 0 262 12307 5 Retrieved 18 November 2018 The first sidewalks appeared around 2000 to 1990 B C in central Anatolia modern Turkey Lendering Jona Royal Road History of Iran Iran Chamber of Society Retrieved 2007 04 09 Boederman John 1997 The Cambridge Ancient History Cambridge University Press p 178 ISBN 978 0 521 22804 6 Horseboating The Horseboating Society Archived from the original on 2018 04 29 Retrieved 2007 04 09 Horses and Canals 1760 1960 The people amp the horses Horse Drawn Boats Canal Junction Ltd Retrieved 2007 04 09 a b Hart Davis Adam 2001 06 01 Roads and surveying Discovering Roman Technology BBC CO UK Retrieved 2007 04 22 Kasem Ajram 1992 The Miracle of Islam Science 2nd ed Knowledge House Publishers ISBN 978 0 911119 43 5 The Rebecca Riots Rebecca and her daughters come to Rhayader Victorian Powys for Schools March 2002 Retrieved 2007 04 28 Theodor Christomannos Die Dolomitenstrasse Bozen Cortina Toblach Chiari Ed Nordpress 1998 ISBN 88 85382 37 1 Roberto Covaz e Annalisa Turel La Costiera triestina storia e misteri di una strada Edizioni Mgs Press Trieste 2006 ISBN 88 89219 23 8 Falbo Nick Annotated Transcript to Protected Intersections for Bicyclists PDF protectedintersection com Retrieved 22 April 2022 a b How wide is a Dutch cycle path 2011 06 29 Laws of New York Vehicle and Traffic Law 152 Valley Post Staff July 5 2021 Overnight 5 Freeway Closure Planned In Burbank For Bridge Construction Burbank Bridge Construction to Shut Down I 5 for Four Nights Beginning July 6 July 1 2021 Kitsap County Road Standards 2006 Kitsap County Washington 2006 Archived from the original Doc on July 9 2006 Retrieved 2007 04 20 Washington State County Road Standards Chapter 35 78 RCW requires cities and counties to adopt uniform definitions and design standards for municipal streets and roads Municipal Research amp Services Center of Washington 2005 Archived from the original on 2007 09 27 Retrieved 2007 04 20 a b c d e f g h Shire of Wyndham East Kimberly October 2006 Guidelines for rural road design and construction technical specifications PDF Western Australia The Last Frontier Archived from the original PDF on 2007 07 10 Retrieved 2007 04 24 Road Building Equipment Constructing roads into forestry work areas Caterpillar 2007 Retrieved 2007 04 20 Volvo Construction Equipment Europe Building the cities towns streets highways and bridges in your neighborhood and in communities around the globe Volvo 2007 Archived from the original on 2006 10 27 Retrieved 2007 04 20 Step by Step Guide How to Lay a Gravel Driveway Mainland Ltd Gravel Driveway Construction at www mainlandaggregates co uk Retrieved 25 Jan 2015 Koerner R M 2012 Designing with geosynthetics 6th Edition Xlibris Corporation US self published source Glossary Princes Highway Traralgon Bypass Planning Assessment Report Archived 2013 05 01 at WebCite at The State of Victoria New active travel schemes Wiltshire Council www wiltshire gov uk Reclaiming city streets for people PDF Milan to reallocate streets to pedestrians and cyclists in bid to reduce air pollution www irishtimes com World cities turn their streets over to walkers and cyclists the Guardian April 11 2020 S Kameyama M Kato A Kawamura K Himeno and A Kasahara August 2002 ISAP 9th Conference Titles amp Abstracts 09044 Effects of Frost Heave on the Longitudinal Profile of Asphalt Pavements in Cold Regions International Society for Asphalt Pavements Archived from the original on 2007 08 13 Retrieved 2007 05 13 a href Template Cite web html title Template Cite web cite web a CS1 maint multiple names authors list link Ron Bridle John Porter 2002 The Motorway Achievement Frontiers of Knowledge and Practice Thomas Telford p 252 ISBN 978 0 7277 3197 5 O Flaherty Coleman A 2002 Highways The Location Design Construction amp Maintenance of Road Pavements Elsevier p 252 ISBN 978 0 7506 5090 8 Newcomb David E Willis Richard Timm David H 2010 Perpetual Asphalt Pavements A Synthesis PDF Lanham Maryland Asphalt Pavement Alliance Retrieved 2013 01 22 Asphalt Pavement Association Perpetual Pavement Award Winners Retrieved 2013 01 22 Theodore R Ferragut Dale Harrington amp Marcia Brink July August 2002 Road Map to the Future United States Department of Transportation Federal Highway Administration Archived from the original on 2007 08 14 Retrieved 2007 05 13 ISG Resources Inc December 2003 Fly Ash Concrete Design for Chicago s 100 Year Road Structure PDF Case Study U S Environmental Protection Agency Retrieved 2007 05 13 Uzarowski Ludomir Maher Michael Farrington Gary Golder Associates Ltd 2005 Thin Surfacing Effective Way of Improving Road Safety within Scarce Road Maintenance Budget PDF Paper for presentation at the 2005 Annual Conference of the Transportation Association of Canada in Calgary Alberta Transportation Association of Canada Archived from the original PDF on 2008 04 07 Retrieved 2007 05 14 Dowel Bars for New and Existing Concrete Pavements PDF Washington State Department of Transportation February 2013 Retrieved 24 March 2014 a b State Aid Concrete Pavement Rehabilitation Best Practices Manual 2006 PDF Archived from the original PDF on 2013 08 09 Retrieved 2013 05 13 Minnesota DOT Practical guidelines for CPR of Urban Roads A compelling need for preserving city concrete streets led to the development of a methodology for scoping repairs and the undertaking of a comprehensive concrete pavement repair program in Grand Rapids Michigan June 2005 Better Roads Minimize Wheel Slap Keep Your Joints Narrow PDF Archived from the original PDF on 2011 07 23 Retrieved 2010 01 06 IGGA How States Preserve Concrete Pavements CPR pays off in extra pavement life Better Roads August 2005 CPR brings dying pavement back to life Georgia continues to be the leader in concrete pavement restoration but as the word spreads other states are beginning to use this system to restore deteriorating pavements April 1997 Roads amp Bridges Magazine Neteler Markus 2007 Open Source GIS A GRASS GIS Approach p 149 Yafeng Yin Jian Lu Wei Wang Icctp 2011 Towards Sustainable Transportation Systems 2011 p 1807 Radu Popescu Zeletin Karl Jonas Idris A Rai e Infrastructure and e Services for Developing Countries 2012 p 141 IEEE ITSS IEEE Intelligent Vehicles Symposium 2005 p 154 Fred Bayles Field Guide to Covering Local News 2012 p 1 Pittsburgh Light Rail Transit Reconstruction Environmental Impact Statement The Administration 1979 Davenport John Davenport Julia L 2006 The Ecology of Transportation Managing Mobility for the Environment Springer Science amp Business Media ISBN 978 1 4020 4504 2 Burton G Allen Jr Pitt Robert 2001 2 Stormwater Effects Handbook A Toolbox for Watershed Managers Scientists and Engineers New York CRC Lewis Publishers ISBN 978 0 87371 924 7 Charles Seawell and Newland Agbenowosi 1998 Effects of Road Deicing Salts on Groundwater Systems Archived 2009 05 21 at the Wayback Machine Virginia Polytechnic Institute Department of Civil Engineering University of Minnesota 2009 U of M research finds most road salt is making it into the state s lakes and rivers 2009 02 10 C Michael Hogan Analysis of highway noise Journal of Water Air amp Soil Pollution Volume 2 Number 3 Biomedical and Life Sciences and Earth and Environmental Science Issue pp 387 92 September 1973 Springer Verlag Netherlands ISSN 0049 6979 Traffic related Air Pollution near Busy Roads American Journal of Respiratory and Critical Care Medicine Vol 170 pp 520 26 2004 Road Dust Something To Sneeze About Science Daily 1999 11 30 Unger N Bond T C Wang J S Koch D M Menon S Shindell D T Bauer S 2010 Attribution of climate forcing to economic sectors Proceedings of the National Academy of Sciences 107 8 3382 87 Bibcode 2010PNAS 107 3382U doi 10 1073 pnas 0906548107 PMC 2816198 PMID 20133724 Ray 2007 Why In Britain Do We Drive On The Left 2Pass co uk Retrieved 2007 03 24 Kincaid Peter 1986 The Rule of the Road An International Guide to History and Practice Greenwood Press ISBN 978 0 313 25249 5 Lucas Brian 2005 Which side of the road do they drive on Retrieved 2006 08 03 Why do some countries drive on the right and others on the left www stat usa gov 2006 02 28 International Market Research Reports Australia CCG 2004 Update Economic Trends and Outlook E Infrastructure Industry Canada Archived from the original on 2007 11 14 Retrieved 2007 04 17 State and Federal Gasoline Taxes Maps Reports and history of gas tax in the United States American Road amp Transportation Builders Association ARTBA Archived from the original on 2007 04 08 Retrieved 2007 05 02 International Bridge Tunnel and Turnpike Association April 16 2007 Retrieved 2007 04 17 Cardno Catherine 2008 Infrastructure New Report Examines the Potential of Public Private Partnerships for Transportation Infrastructure Civil Engineering 78 11 ISSN 0885 7024 Road Transport Europe Overview European Communities Transportation 2007 02 15 Archived from the original on 2007 03 15 Retrieved 2007 03 24 Thruway Fact Book New York State Thruway Authority Archived from the original on 2011 05 02 Retrieved 2011 05 05 Research and Innovative Technology Administration Bureau of Transportation Statistics U S mileage table Archived from the original on 2008 04 18 Retrieved 2012 01 09 National Highways Development Project An Overview PDF Archived from the original PDF on 2014 07 14 Retrieved 2014 06 07 People s Daily Online China to build more highways in 2007 en people cn Expressways Being Built at Frenetic Pace Archived from the original on 1 July 2007 Retrieved 10 January 2017 Tracking Agrica s Progress in Figures PDF African Development Bank 2014 p 71 How to Get Here Nunavut Tourism Canadian Northern Economic Development Agency Retrieved 10 January 2017 Retrieved 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