Assessing the speed impact of urban traffic calming devices using functional data analysis

Excessive driving speed is the most critical factor in road safety. In this context, various traffic calming devices are used on city through-roads. Traditional evaluations have been based on stationary technologies, which does not allow for determining the overall speed impact of traffic calming within speed profile. To fill this gap, we developed the methodology based on the analysis of GPS data by functional data framework. GPS-based speed profiles were used as input for the interval-wise test to assess the statistical significance of speed differences along the road, in the periods before and after the installation of traffic calming devices. The paper presents two studies: (1) a through-road in Sardón de Duero (Spain), where novel road marking was implemented, and (2) eight urban road locations in Czechia, where driver feedback signs were installed. In the Spanish case, statistically significant 6% and 9% speed reductions were detected, as opposed to the Czech locations without any statistically significant speed reductions. In both studies, the average speed along the through-road was not always below the urban speed limit of 50 km/h. This indicates that additional devices are necessary to achieve truly effective traffic calming.