This study includes an analysis of different types of bypass built during the late seventies and during the eighties in regard to effects such as road length, traffic safety, journey times, vehicle costs etc. for urban areas with 2,000-20,000 inhabitants (1990). The bypasses have been divided into three types: (1) Bypass consisting of a new road around the urban area; (2) partial bypass to relieve portions of the urban area of through traffic; and (3) completely new road passing the urban area. One of the projec's primary goals has been to analyse the traffic safety effect of bypasses. For bypasses built during the period 1975-1989 in urban areas which had between 2,000-20,000 inhabitants in 1990, an attempt has been made to analyse the safety situation the years before and after the year of opening. The after situation has thus comprised both the through road and the bypass. The main traffic safety analysis comprises 48 urban areas with 2,000-10,000 inhabitants where bypasses were built during the period 1975-1989. The accident data comprise a period of three years before and three years after the year the bypass was opened. Bypasses have a very positiv effect on the traffic safety situation inside the urban area concerned. The problem is that the accidents occuring after the opening of the bypass on average become more severe, especially the accidents on the bypass. Traffic on the through road has on average varied between 5,000-8,000 motor vehicles per day (24 hours) before the bypass was built. The average length of bypasses is 4,7 km, the partial bypasses are on average 2,6 km and bypass solutions achieved by new roads have an average length of 11,5 km. The largest effect for through traffic is the decrease in journey time as the result of the bypass. The different effects of bypasses described in the report make it possible to evaluate the socio-economic benefit or cost- effectiveness of different types of bypass. (A) For the second part of this study see C 8016 S (IRRD 879179).
Abstract