The Transport and Road Research Laboratory was commissioned by the Department of Transport to assess the safety performance of traffic management systems operated in 1982 at major roadworks on motorways, and to provide indications of how improvements might be made. The study included 23 sites on dual three-lane motorways of traffic controlled by full contra-flow (with two-lane and single-lane crossovers) and by partial contra-flow. In all, studies were made of 241 personal injury accidents (PIA's) at roadworks and 166 PIA's during the same period of a previous year at the same sites but without works. The PIA rate per 1000000 veh-km with works averaged over all traffic management systems was 1.5 times the no-works rate over a length of road thought to embrace all traffic activity associated with the works. Partial contra-flow with a buffer lane was the least safe system, whereas partial contra-flow with a buffer zone was the safest, with full contra-flow lying between. These differences are largely attributable to a relatively high risk of accident when the secondary traffic is operated on the hard shoulder. Because there were fewer fatalities, the accident costs per site of £86,000 With works (1979 prices) were £20,000 less than in the no-works period, though the variability between sites - standard deviation £175,000 - was large. The report also considers the effect of lighting conditions on PIA rates, an association between accidents and breakdowns, and many other accident characteristics. (A)
Samenvatting