Active traffic management (also managed lanes, smart lanes, managed/smart motorways) is a method of increasing peak capacity and smoothing 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, Canada and the United States.
United Kingdom
It is currently in operation on the M42 motorway south-east of Birmingham and in Warwickshire. The scheme had initially been criticised by some due to possible safety and environmental concerns, however a Highways Agency report into the first six months of the scheme showed a reduction in the number of accidents from over 5 a month to 1.5 per month on average. it has now been expanded onto other roads following the initial evaluation on the M42. It is seen as a less expensive alternative to road widening.
Technology
The section of road subject to ATM is monitored by MIDAS sensor loops placed in the road every (which is closer than normal) to observe traffic flows. A computerised system monitors the traffic flows and can set the best speed limit for the current flow of traffic and switch on speed limit signs mounted on gantries up to before an incident. Operators can also monitor 150 CCTV cameras along the route and can control both the speed limits and information signs. Overhead variable message signs can direct drivers to use the hard shoulder during busy periods.
When the speed limit has been lowered to or below the hard shoulder can be opened as an additional lane. To facilitate this and still maintain safety a series of refuge areas have been created around every along that stretch of the road. These take the form of lay bys to the side of the hard shoulder and contain SOS phones within them. In the event of a vehicle breaking down on the hard shoulder, operators can close it, or they can close a lane to allow emergency services access to an accident. 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.
ATM involves converting the hard shoulder into a normal lane during periods of high traffic flow to expand the capacity of the road and may reduce the need to widen motorways. Similar schemes have already been implemented in Europe.
The system makes use of Automatic Number Plate Recognition cameras which to monitor traffic flows and tailor the system. Digital enforcement cameras are also mounted on the gantries and are operated by the West Midlands Police to enforce the mandatory variable speed limits.
Future implementation
Vehicular Ad-Hoc Network
Intelligent Traffic-light Management
In Canada
While active traffic management is currently limited in Canada, more implementation is expected to occur in the future. The QEW highway near Toronto utilizes ramp metering for a portion of the roadway on-ramps.
The city of Toronto has also implemented traffic signal re-timing (signal optimization). Approximately 22 intersections in Toronto now have adaptive signals.
In the province of British Columbia, variable speed limits on overhead gantries have been in use since 2019 on a few highways.
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 35Win Minneapolis, Minnesota and its southern suburbs as part of the Urban Partnership Agreement. Active lane management on I-35W was later combined with high-occupancy toll lanes and eventually joined by a bus rapid transitway. An ATM scheme was deployed on 10 August 2010 in Washington.
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 offences.
ATM systems were activated on of the I-5 northbound carriageway in August 2010. In November 2010, ATM was expanded to of the SR 520 in both directions. In March 2011, ATM completed testing and began operations on of the I-90 in both directions.