To obtain a qualification of a certain traffic intensity on a road carrying only motorised traffic use can be made of some special defined traffic flow levels. If the traffic, however, is mixed with slow traffic then a good qualification is not possible. This is also caused by the lack of suitable capacity data for mixed traffic streams and reliable pcu-values for cyclists, moped riders and different kinds of agricultural vehicles. The quality of the traffic flow depends on the degree of interaction between the vehicles (or the limitation of the mobility of the road users). Given a certain transverse profile and the proposed route of the road, the maintenance of the road surface and weather and lighting conditions, the interaction depends on the composition of the traffic stream, the speed and intensities of the different vehicle modes. By simplifying the reality it has been shown possible to deduce manageable formulas for the calculation of the number of potential simple passages and encounters between two vehicles. The method and the models are described.
Abstract