Road safety assessment in preferential bus lanes through field analysis and microsimulation of traffic conflicts

Preferential bus lanes are a widely use strategy to promote travelers to use public transport instead of private cars. Considering its relevance in the urban transportation planning and operation, it is crucial to evaluate them in terms of the operation and safety externality. We performed a road safety assessment in preferential public transport lanes with complex driving environment using a preventive approach on the 7 th Avenue, in Bogota (Colombia), between 39 th Street and 45 th Street. A detailed study of traffic conflicts was carried out under the guidelines of the Swedish technique, which uses the Time to accident and Conflicting speed to establish the severity of a conflict. A traffic conflict is defined as an incident where, if two road users on collision course maintain their speed and trajectory constant, the crash between them will be imminent. With the field information, we calibrated a VISSIM microsimulation model that correctly replicates its traffic operation. Using the SSAM tool, we validated the base model to identify the simulated traffic conflicts in VISSIM and compared them with the observed conflicts. Under the calibrated environment, we developed and assessed three different scenarios of countermeasures to reduce the number of conflicts observed. As a result, we found that the safest scenario is the one established in the regulations that normalize the operation in preferential lanes, currently not obeyed by most users. Based on our results, we recommend an adjustment in the normative measures, including regulating the stopping time and stopping zones of private vehicles and taxis.