Active Traffic Management

Active Traffic Management (ATM) is a scheme for improving traffic flow and reducing congestion on motorways in Britain. It makes use of automatic systems and human intervention to manage traffic flow and ensure the safety of road users. It is currently in operation on the M42 motorway south-east of Birmingham and in Warwickshire. The scheme has been criticised by some due to possible safety and environmental concerns, however it may now be expanded onto other roads following the initial trial on the M42. It is seen as a less expensive alternative to widening a road.


The Highways Agency's road building budget was £3billion over budget and widening a motorway in the UK costs around £79million as opposed to implementing ATM at a cost of around £5-£15million. It was estimated that widening this stretch of motorway would cost £500million pounds, whereas implementing ATM would cost £100million. It is estimated that it takes 10 years to implement a widening scheme as opposed to 2 years for ATM. Traffic has increased by 80% between 1980 and 2005 whilst road capacity has increased by 10%.

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 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 the 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.

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.

In use

Installation of the first scheme began in November 2004. The first phase, the variable speed limit, came into use on the November 29 2005.The final stage of ATM began operation on the M42 on September 12 2006 between junction 3A for the M40 motorway and junction 7 for the M6 motorway, a distance of . This part of the motorway carries 120,000 vehicles each day made up of long distance traffic, local traffic, customers of Birmingham International Airport and visitors to the National Exhibition Centre (NEC) as well as higher number of accidents than the national average.

The M42 scheme was initially run as an experiment and a Highways Agency report into the first six months of the scheme scheme showed a reduction in journey times of up to 25% The journey time statistics can be broken down to show that northbound journey times were reduced by 26%, equating to an average reduction of 4 minutes as compared to the period when the variable speed limits were on but the hard shoulder was not being used and 9% southbound (equating to 1 minute) during the afternoon rush hour. The report also indicated a fall in the number of accidents from over 5 a month to 1.5 per month on average. The Agency did state that normally accident statistics should be compared over a 3 year period, so the initial results should be treated with caution. They also stated that no accidents had been caused by hard shoulder use as a normal lane. The report also stated that there had been a 10% fall in pollution and 4% fall in fuel consumption. The report also indicated a compliance rate of 98% to the indicated speed limits when using the hard shoulder. For comparison before the introduction of mandatory speed limits at road works, the compliance rate was 10% as opposed to 89% afterwards, showing a similar effect.

The Highways Agency surveyed drivers, stating that 84% felt confident using the hard shoulder, 68% felt better informed about traffic conditions and that around 66% wanted the scheme expanding to other roads.


The Secretary of State for Transport has announced that the government is to introduce the scheme onto two sections of the M6 by 2011 for £150 million. The emergency refuges will be extended to every on the roll out. A further study into the use of ATM on the M1, M4, M20 and M25 motorways was also announced, however the Department for Transport has confirmed that the scheme will not be used on the M25 where the motorway is planned to be widened.


The scheme was initially criticised for exposing people to potentially higher risks in the event of a breakdown or emergency. Environmental campaigners also argued that the scheme would not reduce the environmental impact of motoring. The government was also criticised for introducing the scheme as a cheaper alternative to proper widening.

The Campaign for Better Transport argued that it whilst it would reduce the need for widening schemes, it did nothing to reduce traffic and CO2 emissions. Friends of the Earth criticised the scheme as "widening on the cheap" and also pointed to a possible increase in vehicle emissions. The Highways Agency argue that ATM reduces the environmental impact in regards to widening as it is carried out within the existing boundaries of the motorway as well as a possible improvement in local air quality due to smoother traffic flow.

The RAC cited a study in the Netherlands that showed drivers using the hard shoulder when they were not permitted, increasing the risk of a collision for vehicles stopped. The Royal Society for the Prevention of Accidents also expressed concern that emergency services would take longer to reach an incident. The Highways Agency rejected this concern based on the 5,000 miles of dual carriageway which doesn't have a hard shoulder. Disability groups were concerned that some drivers would not be able to access the emergency phones or even exit their vehicles, leaving them at increased risk.

Ruth Kelly, Secretary of State for Transport stated in an interview that this would not necessarily replace motorway widening in all circumstances, but would be another option and that the government were not using it simply a cheaper method of widening roads.


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