The impact of Active Traffic Management on motorway operation

The Active Traffic Management (ATM) project on the M42 near Birmingham is one of the key and high profile pilot schemes for the Highways Agency (HA) in England. A key feature of ATM is the use of the hard shoulder between J3a and J7 together with variable mandatory speed limits during periods of peak demand (4L-VMSL). The performance of 4L-VMSL has been assessed against the case of three lane motorway with variable mandatory speed limits (3L-VMSL) and against the situation before the implementation of ATM (NOVSL). Based on a 6 month period of data the analysis has shown that: 3/4 4L-VMSL increases the observed capacity of the motorway by an average of 7% (compared to NOVSL) and 10% (compared to 3L-VMSL). 3/4 4L-VMSL reduces the average journey time during periods of recurrent congestion. 3/4 4LVMSL reduces the variability of journey times. On average over all weekdays the variability of journey times under 4L-VMSL has been reduced by 27% and 34% when compared to NO-VSL and 3L-VMSL respectively. This paper outlines the key results that have been obtained from the detailed analysis and identifies the lessons learnt from the evaluation of ATM.