Evaluation and comparison of traffic safety on high standard rural roads.

It is evident that traffic safety on typical rural roads is on average about three times as low as on motorways. But there are different levels of safety on the different types of two-lane roads. In the Federal Republic of Germany there exist two special types of high-standard rural roads: These types of road provide better opportunities for overtaking by means of enlarging the cross-section. One of these types has additional multiple purpose lanes on both sides which can be used temporarily by slower vehicles. The other mentioned variant is an overwide type of rural road. These two types belong to the group of so-called intermediate cross-section roads whose capacity and level of service lies above typical rural roads but below those of the most narrow type of motorways. Intermediate cross-sections are discussed in order to achieve a better safety standard than on rural roads and to avoid some other disadvantages of motorways (mostly environmental aspects). Intermediate cross-sections are regarded as feasible solutions for traffic loads of about 12000 to 18000 veh/day (AADT). For a comprehensive investigation of the intermediate cross-section the German Federal Road Research Laboratory has established an expert team, and has initiated various research activities. Extracted from a detailed full-scale accident analysis (some thousands accidents), which has been carried out by the author, a safety evaluation for the two types of road is intended to be represented. The accident features on these types are also compared with those of typical rural roads and those of motorways to show interrelations between these types concerning traffic safety under different road and traffic conditions.