Previous research on the topic of green arrow signs has mostly been limited to local observations and isolated accidents. This study in contrast was designed to assemble an overview of the current types of application of the green arrow sign. Moreover, it aims to provide updated findings on road safety, conflict potential, and expected benefits of right turns on red that can be generalized. A survey across 75 cities and nine counties came to the conclusion that roughly three quarters of all cities use the green arrow sign. Furthermore, only a quarter of the cities implement all exclusion criteria of the German General Implementation Rules for Road Traffic Regulations (VwO-StVO — traffic code). An inspection of 459 intersections with green arrow signs in Berlin, Dresden, Cologne, Mannheim, and Stuttgart revealed that 22 road accesses were in violation of the VwO-StVO regulations, which could be dangerous especially for non-motorized traffic. The survey also found that 49 cities regularly carry out reviews of accidents at traffic hubs that have green arrow signs installed — ten of which are in line with the traffic code. The remaining 39 cities exhibit deviations in threshold values and the observation period. The analysis of the accidents was two-tiered. Firstly, all cases that occurred at 505 different junctions with traffic lights in Berlin, Dresden, Cologne, Mannheim, and Stuttgart were examined. The varying traffic control setups for right turns were classified into representative categories. This also included analyses of accident sequences at green arrow signs at deliberately chosen junctions in Dresden and Cologne. Secondly, a differentiated analysis of 200 randomly selected junction accesses with varying right turn setups in Berlin and Dresden was undertaken. The analysis showed that junctions with green arrow signs (neglecting objects with protected-permitted right turn signal and triangular islands) exhibit the highest accident and casualty rates, especially when VwO-StVO or [RILSA 1992] criteria for usage of green arrow signs had been violated or right turn lanes existed. With regard to severity of accidents, junctions with green arrow signs do not account for distinct deviations from the mean. Higher rates of casualty and accidents can be traced back to turning onto or off road behaviours as well as above average numbers of non-motorized participants. Cyclist in particular, compared to other forms of right turn participants, are involved in those accidents. The detailed analysis of accidents at 33 junctions in Dresden and Cologne points to similar causes of accidents. Roughly one third of all accidents that can be attributed to green arrow signs involve collisions of green arrow sign users with cyclists or motor vehicles that intersect from the left in possession of right of way. Other factors such as the lack of standard clearance times for pedestrians and cyclists (through signals), reduced sight, and speed limits exceeding 50 km/h on higher priority roads have been identified as infrastructural features that contribute to the risk of accidents. The analysis of road accesses with regard to 1.086 accidents at 150 junctions and 50 T-junctions in Berlin and Dresden only partially supports these findings. Thus, junctions with green arrow signs indeed exhibit higher rates of accidents for turning onto or off of roads or at crossings and involve higher numbers for involvement of non-motorized traffic, but the findings do not show unusual degrees of accidents numbers, accident related costs, or numbers of casualties. Isolated observations of accidents, in which right turning traffic was documented as causing the accident, also do not provide further evidence. Along with the analysis of accidents, traffic observations were conducted in Dresden and Cologne. Documentation and classification of traffic behaviour at 16 junctions with varying setups for right turns were made. Criteria for classification included distinctions between junctions and T-junctions as well as the number of right turn lanes. Moreover, time measurements of traffic with and without green arrow signs were conducted under realistic circumstances. For that purpose, researchers drove frequently occurring path-types under differing conditions and trip times were recorded. Findings prove that most participants used green arrow signs inappropriately; the compulsory stopping at the signal before turning right was only observed sporadically while pedestrian paths and bicycle lanes often were illicitly blocked. Furthermore, intersections with green arrow signs and mixed traffic lanes did not feature increased rates of right turns on red in relation to right turns from mixed traffic lanes and length of red phases. A direct correlation between the use of green arrow signs, on the one hand, and travel time savings as well as limited waiting and stopping time, on the other hand, could not be made. However, a tendency for time savings when green arrow signs were used, whereby the closeness of traffic signals and junctions as well as the portion of junctions with green arrow signs in an area of city played a role, was shown. In summary, the findings show that green arrow sign setups pose threats particularly for non-motorized traffic participants. General correlations, in which the safety of green arrow signs is compared to other right turn forms, cannot be derived from these findings. A general advantage for the traffic flow of motorized traffic was not able to be ascertained in this study. However, it can be assumed that the capacity of an access road can under certain circumstances be increased. Moreover the regulatory requirements are not easily and often not correctly applied. In particular, the threshold values for the review of accidents, which are only used in every fifth city according to our survey, are not practical because the required judicial assessments which frequently involve questions of jurisdiction. (Author/publisher)
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