Road traffic facilities are usually designed on the basis of one specific peak hour (nth hour). Hitherto in Germany, the volume in the 30th hour of the traffic demand duration curve is used. Within the investigation, the suitability of using the 30th hour as the design volume was examined and alternative concepts were analyzed. Based on a stochastic whole-year analysis with the simulation program KAPASIM, congestion-related travel time losses were calculated for 50 cross sections on German federal motorways. In conjunction with the respective trip purposes and travel time unit costs, travel time costs were estimated for each hour of the year. Furthermore, the relationship between the degree of saturation and the congestion-related travel time losses were described by a model function. On sections bearing high volumes of leisure traffic, most of the congestion-related travel time costs occur in the 30 hours of the year with the highest demand. On sections with mainly commuter traffic, time losses are caused even beyond the 300th hour, and the proportion of congestion-related travel time losses during the first 30 hours of the duration curve is between 40 and 80 percent. For the definition of the heavy vehicle percentage in the design hour, using the median value within the span between the (n – 5)th and (n + 5)th hour of the traffic demand duration curve is recommended. Overall, it was found that alternative design concepts do not provide any key benefits in comparison with applying the traffic volume in the nth hour. Regarding the choice of a specific design hour, the differences between the 30th and the 50th hour are relatively small. With regard to a harmonization of European highway design standards, applying the traffic volume in the 50th instead of the 30th hour for highway design can be considered. (Author/publisher)
Samenvatting