Accident data indicate that motorcyclists are a particularly vulnerable group of road users because they run a higher risk of being injured or killed in an accident compared with passenger car drivers. One of the countermeasures that can improve traffic safety for motorcyclists is the increase of the awareness and knowledge about PTWs in planning, construction, operation and maintenance of new and existing roads. In fact, road design standards and policies that regulate design process and safety evaluations are usually based on passenger car characteristics only. In particular, the passenger car operating speed is used as the critical input for design choices of geometric elements connected with traffic safety and as a performance measure to evaluate road design and consistency. Since, unfortunately, the passenger car operating speed might not be representative of the PTW operating speed, this study compared the PTW and passenger car speed distributions in urban areas to establish definitively whether they are similar or not. The results showed that PTW speeds are always considerably higher than passenger car speeds and that the corresponding operating speeds are correlated. Therefore, a prediction equation to estimate the PTW operating speed starting from passenger car operating speed was developed for urban streets. This equation can help highway engineers to estimate expected PTW speed that can be effectively used in the safety evaluations for new and existing roads when the significant presence of PTWs in the traffic flow suggests that this vehicle type should also be considered.
Abstract