Active Traffic Management (ATM)
Variable speed limits and hard shoulder running
Compared to some European countries the UK was slow in developing real-time motorway control techniques like variable speed limits, peak-hour hard shoulder use and active traffic management.
M25 'controlled motorway project'
The UK's first major real-time traffic control scheme was the M25 'controlled motorway project' introduced in 1995 between junctions 12 and 15. This introduced mandatory variable speed limits at busy times and during incidents.
Initially there was some criticism of the M25 scheme as it often imposed confusing speed limits without any explanation. This has improved though with the subsequent introduction of the variable message sign system.
M42 'hard shoulder running' pilot
The M42 'hard shoulder running' pilot scheme between junctions 3a and 7 near Birmingham aimed to build on the M25 scheme and uses state-of-the-art, real-time traffic management to improve traffic flow and safety.
The M42 scheme, which started in September 2006, uses high-tech systems to measure traffic speed/flow and activate various traffic control measures like variable speed limits, lane control and use of the hard shoulder.
The controlled section of motorway is intensively signed with 50 gantries, 250 variable signs, emergency refuges every 500 metres which detect broken down vehicles, and CCTV.
Results of the M42 pilot
The M42 ATM scheme has proved very successful. It has;
- Reduced congestion,
- Improved journey times, and
- Provided a more comfortable driving experience.
Users have said they prefer the system to be switched on all the time and the vast majority say they understand the signs.
However, the safety of the system is totally dependent on drivers adhering to the 'controls' – the most vital of which is the red cross over the hard shoulder which means it is closed to running traffic.
The hard shoulder must also not be used when the ATM system is off i.e. when variable speed limits and congestion signs are not lit.
AA views
The AA supports the Active Traffic Management scheme on the M42 as it has gained drivers' support, eased congestion, improved journey reliability and made driving more comfortable.
The Department for Transport's decision (announced by Secretary of State, Ruth Kelly on 25 October) to consider extending the scheme to other motorways is welcome but the AA makes the following observations:
- Operationally there have been no problems for AA patrols helping members – in fact ATM has worked well
- Usually it takes 3 years worth of data to determine the success of a major scheme but this one has produced such good initial results it is worth taking forward
- ATM improves capacity and makes driving more comfortable in peak traffic and it also encourages better lane discipline
- Planners must guard against over development alongside the M42 which will dilute the benefit by adding more traffic
ATM is not though a solution applicable to all UK motorways
- There is still a need for more robust, traditional widening with hard shoulders on some overloaded sections of motorway
- ATM was five times cheaper than widening the M42 so there is no reason to simplify ATM controls to save money if it is to be used elsewhere – ATM works because it has an array of safety systems built in.
- UK drivers pay £45 billion in road tax and deserve the most robust solutions to motorway congestion – ATM should not be used to save money on proper widening but it has major potential to lock in the benefits of widening and provide relief at specific peak hour hot-spots.
For more information
More detail from the Highways Agency about Active Traffic Management.
Ruth Kelly's announcement on 25 October 2007
The Highways Agency has produced an animated drive through to show how Active Traffic Management works in practice.
The Highway Code published on the Directgov website includes more detailed information about the traffic control signs used.
1 November 2010