In traffic engineering, a merge is the point where two streams of traffic travelling in the same direction from multiple roads or in multiple lanes on the same road are required to merge into a single lane.
Two lanes merging into one
A merge may be a permanent road feature, for example at the end of a dual carriageway, or a temporary feature, common during roadworks.
Generally speaking, at a slip road onto a controlled-access highway or otherwise, traffic on the highway has priority over traffic joining at the slip road, and therefore the slip road traffic should accelerate to the speed on the major road and merge into a gap in the stream of traffic in lane one. At some slip roads, traffic continues into a new lane (a "lane gain") and therefore does not need to merge.[1]
Early mergeEdit
A variable message sign warning drivers of a lane closure on the M25
The early merge method dictates that one stream of traffic will maintain priority over another at the merge, and therefore traffic in the other lane should merge at the first opportunity. To encourage drivers to merge early, authorities may employ a static or dynamic early merge strategy. Strictly speaking an early merge is different from a conventional merging method, in that the traffic is encouraged to merge well in advance of the merge point.[2]
A static early merge strategy involves the placement of advance notices for a fixed distance in advance of the lane closure. This method may reduce the chance for rear-end collisions by warning drivers of the closure in advance of congestion.[2]
A dynamic merge strategy involves advance notices for a variable distance from the lane closure. For example, in the US state of Indiana, a dynamic no-passing zone is created in advance of the merge, to ensure drivers can move into the open lane before reaching the end of a queue.[2]
Late mergeEdit
A 'Queue in both lanes' sign instructs drivers to use both lanes up to the merge pointZipper method road signage in Warsaw
The late merge method dictates that both streams of traffic should continue to drive up to the point of closure, and merge at the marked taper. Both streams should create alternating gaps into which vehicles from the other stream can merge at the merge point. In heavy traffic flow, traffic should therefore queue in both lanes in advance of the merge.[2]
The late merge method has not been found to increase throughput (throughput is the number of vehicles that pass through a point in a given period of time). However, it considerably reduces queue ("backup") length (because drivers use the ending lane until its end) and reduces speed differences between the two lanes, increasing safety.[3] The late merge operates at a nearly 20 percent higher capacity than a conventional merge.[2] In the case of Interstate 77 in North Carolina, where signs directed people to use the zipper[clarification needed] merge, the maximum length of the backup was reduced from eight miles to two.[4]
A possible dynamic merge method would use variable message signs to instruct drivers to use all available lanes and to merge in turn if queueing is detected. At other times, drivers would use a conventional merging method.[2]
Governments hold campaigns to promote the late merge method because irritation and aggression are common among drivers who are not educated about the benefits of the technique, sometimes including straddling lanes to block late mergers. Often drivers who change lanes too early do not like to see other drivers continue until the end of the drop-away lane, even though this late merging is encouraged by the authorities.[5][additional citation(s) needed]
In various jurisdictionsEdit
In most countries, a driver can be penalized for not using the late merge method, but in some countries only where a traffic sign so indicates.[citation needed]
Under the Highway Code, drivers should not use the right lane except when overtaking other vehicles, therefore they should move back to the left-hand lane as soon as it is safe to do so (Rule 137). The Code does however recommend merging in turn if it is safe and if vehicles are travelling at a very low speed (Rule 134).[7]
United StatesEdit
Most states in the United States require merging traffic to yield to through traffic which already exists in the lane they wish to enter.[citation needed] This further complicates the common understanding of proper merging protocol, as even though zipper merging is widely encouraged, those doing so are still legally required to yield, and those who choose not to let them merge are not doing anything wrong from a legal standpoint. Traffic already in the lane being merged into has the right of way over the merging traffic from the lane that will disappear.
^"Zipper Merge | Missouri Department of Transportation". www.modot.org. Retrieved 2021-12-31.
^Pennsylvania Department of Transportation (2013). Publication 236: Handbook of Approved Signs(PDF). Retrieved 2023-06-13. Signs G70-1 "Use Both Lanes to Merge Point Sign" and G70-2 "Merge Here Take Your Turn Sign".
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For other uses of the term merge see Merge disambiguation In traffic engineering a merge is the point where two streams of traffic travelling in the same direction from multiple roads or in multiple lanes on the same road are required to merge into a single lane Two lanes merging into oneA merge may be a permanent road feature for example at the end of a dual carriageway or a temporary feature common during roadworks Contents 1 Methods 1 1 Slip road 1 2 Early merge 1 3 Late merge 2 In various jurisdictions 2 1 Canada 2 2 United Kingdom 2 3 United States 3 See also 4 References 5 Further reading 6 External linksMethods EditSlip road Edit Generally speaking at a slip road onto a controlled access highway or otherwise traffic on the highway has priority over traffic joining at the slip road and therefore the slip road traffic should accelerate to the speed on the major road and merge into a gap in the stream of traffic in lane one At some slip roads traffic continues into a new lane a lane gain and therefore does not need to merge 1 Early merge Edit nbsp A variable message sign warning drivers of a lane closure on the M25The early merge method dictates that one stream of traffic will maintain priority over another at the merge and therefore traffic in the other lane should merge at the first opportunity To encourage drivers to merge early authorities may employ a static or dynamic early merge strategy Strictly speaking an early merge is different from a conventional merging method in that the traffic is encouraged to merge well in advance of the merge point 2 A static early merge strategy involves the placement of advance notices for a fixed distance in advance of the lane closure This method may reduce the chance for rear end collisions by warning drivers of the closure in advance of congestion 2 A dynamic merge strategy involves advance notices for a variable distance from the lane closure For example in the US state of Indiana a dynamic no passing zone is created in advance of the merge to ensure drivers can move into the open lane before reaching the end of a queue 2 Late merge Edit nbsp A Queue in both lanes sign instructs drivers to use both lanes up to the merge point nbsp Zipper method road signage in WarsawThe late merge method dictates that both streams of traffic should continue to drive up to the point of closure and merge at the marked taper Both streams should create alternating gaps into which vehicles from the other stream can merge at the merge point In heavy traffic flow traffic should therefore queue in both lanes in advance of the merge 2 The late merge method has not been found to increase throughput throughput is the number of vehicles that pass through a point in a given period of time However it considerably reduces queue backup length because drivers use the ending lane until its end and reduces speed differences between the two lanes increasing safety 3 The late merge operates at a nearly 20 percent higher capacity than a conventional merge 2 In the case of Interstate 77 in North Carolina where signs directed people to use the zipper clarification needed merge the maximum length of the backup was reduced from eight miles to two 4 A possible dynamic merge method would use variable message signs to instruct drivers to use all available lanes and to merge in turn if queueing is detected At other times drivers would use a conventional merging method 2 Governments hold campaigns to promote the late merge method because irritation and aggression are common among drivers who are not educated about the benefits of the technique sometimes including straddling lanes to block late mergers Often drivers who change lanes too early do not like to see other drivers continue until the end of the drop away lane even though this late merging is encouraged by the authorities 5 additional citation s needed In various jurisdictions EditIn most countries a driver can be penalized for not using the late merge method but in some countries only where a traffic sign so indicates citation needed nbsp Sample British Columbia signage sign C 138 TF Canada Edit British Columbia s sign manual provides designs for zipper merge signs 6 United Kingdom Edit Under the Highway Code drivers should not use the right lane except when overtaking other vehicles therefore they should move back to the left hand lane as soon as it is safe to do so Rule 137 The Code does however recommend merging in turn if it is safe and if vehicles are travelling at a very low speed Rule 134 7 United States Edit Most states in the United States require merging traffic to yield to through traffic which already exists in the lane they wish to enter citation needed This further complicates the common understanding of proper merging protocol as even though zipper merging is widely encouraged those doing so are still legally required to yield and those who choose not to let them merge are not doing anything wrong from a legal standpoint Traffic already in the lane being merged into has the right of way over the merging traffic from the lane that will disappear Minnesota 8 and Missouri 9 recommend that drivers zip merge Pennsylvania s sign manual provides designs for zipper merge signs 10 See also EditFilter in turnReferences Edit Motorways Joining the motorway 259 THE HIGHWAY CODE Retrieved 2021 09 13 a b c d e f Dynamic Late Merge Control Concept for Work Zones on Rural Freeways FHWA Work Zone ops fhwa dot gov Retrieved 2021 09 13 Johnson Ken Late Merge the Zipper System PDF Minnesota DOT Retrieved 30 April 2013 Boyle John 7 July 2019 Is the zipper merge a sensible system or just infuriating Asheville Citizen Times Retrieved 7 July 2019 The Zipper Merge May Seem Aggressive But It s Actually A Highway Congestion Reliever British Columbia Ministry of Transportation and Infrastructure 2022 Standard Traffic Signs Construction Signs PDF C 137 and C 138 Series Multi lane carriageways 133 to 143 THE HIGHWAY CODE Retrieved 2021 09 13 Zipper Merge MnDOT www dot state mn us Retrieved 2021 12 31 Zipper Merge Missouri Department of Transportation www modot org Retrieved 2021 12 31 Pennsylvania Department of Transportation 2013 Publication 236 Handbook of Approved Signs PDF Retrieved 2023 06 13 Signs G70 1 Use Both Lanes to Merge Point Sign and G70 2 Merge Here Take Your Turn Sign Further reading EditVanderbilt Tom 2008 Traffic why we drive the way we do and what it says about us Knopf pp 3 5 46 50 309 ISBN 978 0 307 39772 0External links Edithttp www dot state mn us zippermerge Retrieved from https en wikipedia org w index php title Merge traffic amp oldid 1165267630, wikipedia, wiki, book, books, library,
