The Department for Transport has confirmed that widening schemes planned for the M6, M1 and M25 won’t be affected by new congestion-busting proposals for lower peak time variable speed limits (between 40mph and 60mph) and use of hard shoulders during peak periods.

The Government will initially extend trials of active traffic management schemes within the Birmingham “motorway box” covering the M6 and M42 following the success of the first scheme on the M42, while a DfT spokesman admitted “it could well spread out to other high congestion areas as part of a feasibility study”.

Initial camera-controlled M42 trials on an 11-mile section east of Birmingham generated more than 95% speed limit compliance.

Fuel consumption and vehicle emissions fell by 4% and 10% respectively in trials, which also included the south-west M25. Future studies could use different graduated limits for different lanes.