Interchanges of Rural Roads


Evaluation of Traffic Quality in Plan-Free, Partially Plan-Free and Partially Plan-Equal Intersections of Rural Roads

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In the context of this survey, a traffic quality analysis of grade-separated, partially grade-separated and partially at-grade intersections at rural roads was carried out. The basis for this was formed by a literature analysis about influence parameters on traffic quality as well as measurements at real intersections and a simulation study at standardized intersections via microscopic traffic flow simulation.

For grade-separated and partially grade separated intersections, the procedures for evaluating traffic quality in merge and diverge areas according to the draft of the HBS (201X) were analyzed for their applicability on the basis of the measurement results. Due to an extensive qualitative compliance of the determined quality levels with the observations from the surveys, an applicability of the procedures can be assumed.

For partially grade-separated and partially at-grade intersections, an essential aim of the survey was to investigate the occurrence of interactions between at-grade intersections and their impact on traffic quality as well as, based on this, to develop procedures for a summarizing assessment.

According to the study results, the procedures of HBS to determine the waiting times and to measure the storages can be applied separately for the at-grade intersections. Excluded from this are partially grade-separated intersections with two roundabouts in which interactions between the intersections elements were identified that were connected in the simulation with lower waiting times than stated in the HBS. A correction factor was derived by which the calculated waiting times of a single roundabout could be adjusted and by which the observed interactions between two roundabouts could be taken into account.

The gained findings and the derived approaches allowed concretizing and expanding the application areas of the HBS procedures (201X) for intersection elements with and without signalization in the area of partially at-grade and partially grade-separated intersections with regard to a summarizing assessment. From the simulation results also findings about mean vehicle driving speeds in the area of partially at-grade and partially grade-separated intersections could be derived, which are of importance with regard to the determination of mean vehicle driving speeds on net sections of rural roads.



Federal Ministry of Transport and Digital Infrastructure, represented by the Federal Highway Research Institute


Dipl.-Ing. Andreas Klein

Year of Completion