Modelling cyclists‘ behaviour and interactions at urban intersections

Kurzfassung

The number of cyclists in Germany is increasing yearly, but infrastructure has failed to adapt to this growth. E-bikes are becoming more common, resulting in more speed differences on bicycle paths. In addition, manoeuvrable e-scooters and large cargo bikes also share the bicycle path with conventional bicycles and e-bikes. Bicycle paths are mostly narrow and it is difficult to manoeuvre without interaction with other cyclists. Little is known about the causes of bicycle-bicycle accidents. Due to the limited availability of accident data, real-life observational data can be used to gain a better understanding of bicycle-bicycle interactions. This dissertation aims to provide a more comprehensive understanding of how cyclists interact with each other by presenting an overview of interaction patterns, descriptions of interactions, and initial modelling approaches. The data used for this thesis were collected over several weeks at different intersections in Braunschweig, Germany. At these intersections, the trajectories of road users were recorded by using camera systems. The thesis demonstrated that there are three primary categories of cycle interactions at intersections: overtaking, oncoming, and crossing. Surrogate Measures of Safety were utilised as criticality metrics to assess the degree of criticality of the interactions between cyclists in the scenarios. Route choice, speed during the interaction, lateral distances during the interaction and longitudinal distances before the interaction were analysed in order to subdivide the oncoming and crossing scenarios into further sub-scenarios. In addition, it was investigated how often cyclists adhere to the rules in the observation data (correct direction of travel, respecting right-of-way, bicycle path use) and how they themselves rated their cycling behaviour in a survey. The results of the analysis demonstrate that instances of deviant behaviour in particular can precipitate critical situations. The observed bicycle path is notably narrow, rendering it difficult for two cyclists to ride side-by-side. In the event that a cyclist travels in the incorrect direction on the bicycle path, there is an inherent risk of collision with another cyclist travelling in the wrong direction. Such an incident could result in injury. It is therefore of the utmost importance to educate children at an early age about cycling rules. Signs, pictograms or additional illuminations in critical areas of a bicycle path can alert cyclists that they are cycling in the wrong direction. In the crossing scenario, the installation of additional traffic lights could be considered to clarify the right-of-way. The study underlines the serious potential of conflicts of cyclists at intersections and the need for further research in this area. Parameter distributions can be used in the future to develop measures for mitigating cyclist conflicts or to simulate and plan infrastructure more effectively and safely.