Since 1980, roads are labelled traffic calming zones (Verkehrsberuhigter Bereich, VBB) with traffic sign 325 of the German Highway Code (Strassenverkehrsordnung, StVO). Increasing road safety, improving quality of stay, and environmental aspects have remained topical reasons for this type of traffic calming measure until this day. Traffic calming zones aim to achieve equality among road users. Both the speed of vehicles and the amount of motor traffic should be reduced. Consistent design rules for traffic calming zones were previously inexistent, whereby design elements such as mixed traffic areas and a level expansion within the Administrative Regulation of the German Highway Code (Verwaltungsvorschrift zur Straßenverkehrsordnung, VwV-StVO) — amongst other things — are recommended. In practice, there is a wide field of application for traffic calming zones. Alongside the application area of residential streets that was originally envisaged, nowadays, traffic calming zones with traffic sign 325 StVO can also be found in inner city residential areas, access roads and, more and more frequently, in commercial streets. Furthermore, there are numerous special application areas for traffic sign 325 StVO in practice, such as parking areas, for example. Although traffic sign 325 StVO was introduced into the StVO as early as 1980, the only scientific studies on the impact on traffic flow and the occurrence of accidents date back to the early 1980s. More recent studies are not available, despite traffic sign 325 StVO finding more and more widespread use. The current study initially observed accidents in traffic calming zones with traffic sign 325 StVO based on official nationwide statistics. Furthermore, detailed accident analyses of almost 300 practical VBB examples as well as traffic flow analyses from more than 200 hours monitoring in 50 selected traffic calming zones were performed. Overall, it was established that the occurrence of accidents in all areas monitored is inconspicuous, and that as a rule, traffic calming zones with traffic sign 325 StVO can be classified as safe for traffic. Equally, the analyses of traffic flow monitoring demonstrated that there were no significant uncertainties to be observed. However, it must be stated that the average speed in traffic calming zones in parts significantly exceeds the permissible walking speed of 7 km/h. This applies to both motor and bicycle traffic. In addition, traffic flow regulations regarding the transition from traffic calming zones to adjacent road networks do not seem to be clear-cut for some road users. Here, depending on local conditions, different "right-of-way regulations" are implemented by road users. In conclusion, it can be said that in practice, due to its diverse design possibilities, a traffic calming zone with traffic sign 325 StVO is often even difficult to recognise within the same municipality on the basis of its design. (Author/publisher)
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