Following pressure by a number of groups in the USA to raise the speed limit on roads, legislation was enacted in 1987 to allow a maximum speed limit of 65 mph on interstate highways outside urban areas of 50,000 or more population. By the end of 1988, 40 states had raised the limit and this paper describes the studies that were thus made possible to monitor the effects of increasing speed limits. Data is presented from New Mexico, Virginia, Maryland and 11 north-eastern states some of which, like Maryland, retained the 55 mph limit. Sampling was restricted to free-flowing vehicles with a headway of at least 5 seconds using k-band radar devices. The percentage of passenger cars exceeding limits and 85th percentile speeds are shown together with information on fatalities. The results showed how speed is strongly influenced by the posted limits. The percentage of motorists travelling at high speeds increased dramatically and fatalities increased by between 20 - 30%. Despite the overwhelming evidence of negative effects, no plans exist to lower limits. For the covering abstract of the conference see IRRD 843582.
Samenvatting