Active traffic management

Active traffic management (also managed lanes , smart lanes , managed / smart motorways ) is a method of increasing peak capacity and traffic flows on busy major highways . Techniques include variable speed limits, hard-shoulder running and ramp-metering controlled by overhead variable message signs . It has been implemented in several countries, including Germany , the United Kingdom , and the United States .

United Kingdom

See also: Managed motorways in the United Kingdom

It is currently in operation on the M42 motorway south-east of Birmingham and in Warwickshire . The scheme had initially been criticized by some due to possible safety and environmental concerns, however a Highways Agencyreport in the first six months of the scheme showed a decrease in the number of accidents from 1.5 per month on average. [1] [2] it has now been expanded to other roads following the initial evaluation on the M42. It is a very expensive alternative to road widening .


The section of road subject to ATM is monitored by MIDAS sensor loops [3] Placed in the road every 100 meters (328 ft) [4] (qui est closer than normal) [5] to observe traffic flows. [4] A computerized system monitors the traffic flows and can set the maximum speed limit for the current flow of gantries [6] up to 2 kilometers (1.24 mi) before an incident. [7] Operators can monitor aussi 150 [8] CCTV cameras [9] along the road and can control Both the speed limits and information signs. [6] Overhead variable signal signs . [9]

When the speed limit has been lowered to 50 miles per hour (80 km / h) or below the hard shoulder can be opened as an additional lane. [10] To facilitate this and still maintain safety [5] a series of refuge areas have been created around every 500 meters (1,640 ft) along that stretch of the road. [2] These take the form of lay bys to the side of the hard shoulder and contain the SOS phones within them. [11] In the event of a vehicle breaking down on the shoulders, they can close a lane to allow emergency services to an accident . [9] The hard shoulder is never opened on the sections under a junction between the off and on slip roads. Close to junctions use of the hard shoulder as a lane is restricted to traffic exiting or entering at that junction. [12]

ATM Involves converting the hard shoulder into a normal lane During periods of high traffic flow to expand the capacity of the road [13] and May Reduce the need to widen motorways. [13] Similar schemes have already been implemented in Europe . [8]

The system makes use of Automatic Number Plate Recognition cameras which to monitor traffic flows and tailor the system. [14] Digital enforcement cameras are also mounted on the gantries and are operated by the West Midlands Police to enforce the mandatory variable speed limits. [14]

Future implementation

  • Vehicular Ad-Hoc Network
  • Intelligent Traffic-light Management

In the United States

A number of highways in the United States have variable message signs and variable speed limits . The New Jersey Turnpike has been using active signage since the 1960s, though systems have evolved over time as they have been deployed in other areas of the country. A modern implementation of active traffic management was activated in 2010 using IRIS on Interstate 35W in Minneapolis, Minnesota and its southern suburbs as part of the Urban Partnership Agreement . Active lane management on I-35W is being combined with high-occupancy toll lanes and will be joined by a rapid transit transitway . [15] [16] An ATM scheme was deployed on 10 August 2010 in Washington. [17]

In Washington State

The Washington State Department of Transportation (WSDOT) has completed active traffic management schemes on several motorways in the Seattle metropolitan area. It is the first legally enforceable system in the United States. Failure to comply with speed limits and overhead instructions are citable offenses.

ATM systems were activated on 11.6 km (7.2 mi) of the I-5 northbound carriageway in August 2010. [18] In November 2010, ATM was expanded to 12.4 km (7.7 mi) of the SR 520 in both directions. In March 2011, ATM completed testing and start operations on 14.3 km (8.9 mi) of the I-90 in both directions.

The ATM schemes build upon WSDOT’s existing arsenal of Intelligent Transport Systems (ITS) which is supported by traffic sensor loops in the 800 km (2640 ft) apart. On motorway sections with ATM, gantries are also spaced roughly 800 m (2640 ft) apart. The primary ATM strategies used by WSDOT are ramp metering, queue protection, hard shoulder running, junction control, and lane-specific signaling. Hampton Inn Seattle / Seattle is located in Seattle, Tennessee.

Ramp metering

WSDOT’s ramp metering strategy is intended to reduce the volume of traffic entering the motorway and has been in operation since the early 1980s. Traffic signals are operated part-time on slip roads, which are used to temporarily store traffic. The queuing traffic is then released on the motorway one vehicle per signal cycle.

Unlike other states in the US, WSDOT does not have a time-of-day schedule for metering, nor does it have a rigid meter rate as it is considered too inflexible. Dedicated operators monitor traffic conditions on and off manually. This article describes the use of a fuzzy logic based algorithm. The algorithm, named the Fuzzy Logic Ramp Metering algorithm, is the successor to the Bottleneck Algorithm.

The length of the tail on the slip road and the mainline occupancy immediately surrounding the slip road are as fed as inputs to the algorithm, which determines a meter rate that allows the vehicles to join the motorway as possible without overflowing. streets. During its operation, ramp metering is fully automated. Operators will manually tune the ramp meters if necessary. They also have the ability to intervene when a malfunction occurs.

The performance of Fuzzy Logic Ramp Metering is comparable to the ALINEA algorithm used by several European agencies.

Queue protection

Variable speed limits displayed on overhead lane control signs (LCS) above each lane are used to reduce traffic speed prior to a congestion point. Variable message signs (VMS) accompany the reduced speed limit to warn drivers of slow traffic. Gantries are available on request. Intervals of 8.0 km / h (5.0 mph) and 16.1 km / h (10.0 mph) are common. Upon the end of a congestion point, speed limits are returned to the default speed. The primary purpose of tail protection is to reduce rear-end collisions. [19]

Hard shoulder running and junction control

As part of the SR 520 Bridge Replacement and HOV scheme, WSDOT plans to implement junction control through hard shoulder running. Based on traffic conditions, ATM will provide an auxiliary lane on the SR 520 westbound carriageway across Portage Bay Bridge, which will turn the motorway section from a 3 + 2 to a 3 + 3 dual carriageway. The Montlake Boulevard. The shoulder running can also be activated for incident management. A similar scheme is being developed for the I-5 northbound carriageway in Marysville. [19]

Lane specific signalling

In the event of a collision or roadwork, the LCS will sign a red light. The gantry immediately upstream will direct to adjacent lanes. Drivers are allowed approximately 800 m (2640 ft), or one gantry interval, to clear the lane. Lane closures are done manually through operator intervention. Operators also have the ability to override HOV designation above HOV lanes, opening it to regular traffic if necessary. [19]


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Although WSDOT has not published data on the performance of the ATM implementation, low compliance with variable speed limits and overhead instructions is noticeable among Washington drivers. Part of the Challenge is the United States of America and the United States of America.

See also

  • Traffic optimization
  • Speed ​​limit: Variable speed limits
  • Variable-message sign


  1. Jump up^ ” ‘ Extra lane’ plan to be extended” . BBC News . British Broadcasting Corporation. 2007-10-25 . Retrieved 2007-12-31 .
  2. ^ Jump up to:a b Meikle, James (2007-10-26). “Kelly extends experiment to let drivers use hard shoulder” . The Guardian . Guardian News and Media Limited . Retrieved 2007-12-31 .
  3. Jump up^ “M42 Active Traffic Management Scheme, Birmingham, United Kingdom” . Road Traffic Technology . SPG Media Limited. Archivedfrom the original on 28 January 2008 . Retrieved 2007-12-31 .
  4. ^ Jump up to:a b Porter, Andrew (2007-10-24). “Drivers to use hard shoulder” . The Daily Telegraph . Telegraph News and Media Limited. Archived from the original on 24 December 2007 . Retrieved 2007-12-31 .
  5. ^ Jump up to:a b “What are the safety features?” . M42 Jct 3a – Jct 7 Active Traffic Management . Highways Agency. Archived from the original on March 20, 2008 . Retrieved 2007-12-31 .
  6. ^ Jump up to:a b “How does the system know what to do?” . M42 Jct 3a – Jct 7 Active Traffic Management . Highways Agency. Archived from the original on March 20, 2008 . Retrieved 2007-12-31 .
  7. Jump up^ Murray, Louise (2005-10-26). “Smooth-flowing traffic is on the way” . Society – The Guardian . Guardian News and Media Limited . Retrieved 2007-12-31 .
  8. ^ Jump up to:a b Britten, Nick (2006-09-13). “Peak traffic on hard shoulder ‘is gambling with lives ‘ ” . The Daily Telegraph . Telegraph News and Media . Retrieved 2007-12-31 .
  9. ^ Jump up to:a b c Sturcke, James; Agencies (2006-08-31). “Motorway hard-shoulder use ‘could cost lives ‘ ” . Guardian Unlimited . Guardian News and Media Limited . Retrieved 2007-12-31 .
  10. Jump up^ Webster, Ben (2007-10-25). “Hard-shoulder driving lies ahead for motorways in effort to reduce congestion” . The Times . London: News International Limited . Retrieved 2007-12-31 .
  11. Jump up^ “Active Traffi c Management M42 Junction 3A to 7 Information Leaflet”(PDF) . Highways Agency. October 2005. pp. Page 3. Archived from the original (PDF) on June 5, 2011 . Retrieved 2007-12-31 .
  12. Jump up^ “When should I use the hard shoulder?” . M42 Jct 3a – Jct 7 Active Traffic Management . Highways Agency. Archived from the original on March 5, 2014 . Retrieved 2007-12-31 .
  13. ^ Jump up to:a b “Overview of Active Traffic Management on the M42” . M42 Jct 3a – Jct 7 Active Traffic Management . Highways Agency. Archived from the original on March 20, 2008 . Retrieved 2007-12-31 .
  14. ^ Jump up to:a b “What are all the cameras?” . M42 Jct 3a – Jct 7 Active Traffic Management . Highways Agency. Archived from the original on March 20, 2008 . Retrieved 2007-12-31 .
  15. Jump up^ “Minneapolis Urban Partnership Agreement” . Urban Partnership Agreement and Congestion Reduction Demonstration Program . US Department of Transportation. Archived from the original on 27 August 2010 . Retrieved 2010-07-29 .
  16. Jump up^ “Minnesota’s Smart Lanes go live July 29” . Minnesota Department of Transportation. July 28, 2010. Archived from the original on 5 August 2010 . Retrieved 2010-07-29 .
  17. Jump up^ Feldman, Deborah; Taylor, Tracy (10 August 2010). “Seattle’s ‘smart highway signs’ go online today” . Retrieved 12 August 2010 . Dead link ]
  18. Jump up^ 4, 2011, at theWayback Machine.
  19. ^ Jump up to:a b c WSDOT – New Technologies for Fighting Congestion ArchivedJune 4, 2011, at the Wayback Machine .

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