Center for Spatial Studies

Increasing in-town bicycle traffic creates a demand for safe and efficient transportation infrastructure. A significant safety aspect is crossroad layout. Existing solutions such as protected crossroads, roundabouts and standard four-way crossings are investigated in terms of viewing angles between traffic participants. An agent-based simulation helps to generate data, which is further analysed. Special attention is paid to blind spots of vehicles during turns, overall line of sight and human field of view. We can show that especially protected crossroad designs have major advantages. Standard layouts convince in terms of the analysed field of view and possible blind spots. However, they demand extensive shoulder views and head turning especially during right turns. This makes them less safe. Roundabouts show medium results. Exiting this structure always requires a right turn which is, in terms of visibility, the most dangerous action for bicycles. We conclude that protected crossroads can be recommended as the safest approach in comparison to standard and roundabout layouts. Yet, space requirements may restrict in-town realization of this design.