Recommendations for the adjustment of existing rural roads towards self explaining roads

Within the project design of rural roads by normalized road characteristics (Richter & Zierke 2008) the TU Berlin was researching which road design will affect driving behavior and road safety in a positive way. The project aims are to provide self-explaining and recognizable roads and therefore increase road safety by creating design classes. Based on detailed accident analysis´ the design classes were derived. The design classes consist of a suitable combination of cross-section and junction designs. Other considerations within the deliberations of safe design classes were the form of operation and the alignment. The evaluation of the roads was carried out by the driving behavior. The driving behavior was examined in with/without and before/after situations on real roads. The empiric analysis contained over 10,000 km on roads with the following-car technique. Furthermore, the detected self-explaining roads were analyzed in the driving simulator of the TU Berlin. To ascertain the effect of these types of roads they were compared with real roads which were implemented into the driving simulator. The results of the project show that the driving behavior and therefore the road safety are influenced by the road design. Overall, appropriate combinations of cross-sections and junctions with the alignment in mind affect the driving speed and lane keeping positively. For example the implementation of roundabouts reduced the driving speed on regular two lane rural roads (the design class 3) not only within the sphere of intersections but also in the open road sections. Another major task was the analysis of the influence of a new cross section design for low-volume roads. A before/after study showed that the driving behavior on these roads can be affected positively by implementing the new cross section design; a reduced speed was determined and passing situations with oncoming traffic did not seem to cause problems. Based on these detailed empiric analysis recommendations for planners are given within the project to ensure the correct effects of the adjustments towards self-explaining roads.