Traffic impacts of shared right-of-way public transport systems: A microsimulation-based case study

Abstract

Bus Rapid Transit systems are becoming a more integral part of public transport systems in major African cities. Although BRT systems are more versatile than other public transport alternatives, they do require support from other transport systems. Due to geographic limitations and varying transport demand, a BRT system can only function optimally if it is well integrated with the surrounding transport network. In the case of most African transport networks, the informal modes serve as the foundation of the system. In South African cities the minibus taxi is responsible for over 60% of the daily passenger trips. It is evident that in order for a BRT system to function within the African context, a synergistic relationship between the BRT and minibus taxi must be found. The interaction between BRT and minibus taxis is diverse and cannot be captured in one individual study. The aim of this study is to look at the traffic flow performance of road networks which operate under varying hybrid scenarios. These hybrid scenarios consist of varying configurations where minibus taxis and BRT buses are expected to use the same infrastructure. Specifically, the question is what the implications would be of using existing BRT infrastructure in a shared operational model. Traffic flow performance is calculated and measured by means of a microsimulation model which simulates various hybrid (between taxis and BRT) conditions. Currently very limited detailed information is available about the interaction of these public transport modes. Modelling a calibrated microsimulation provides detailed insight into the interaction of minibus taxis and BRT buses and allows the testing of various experimental scenarios which have yet to be examined. The microsimulation and the data extracted from its analysis provides information about the individual performance of buses, minibus taxis and passenger vehicles. This provides decision makers with important data which can be used to optimise the network for the desired transport modes. The microsimulation also indicates a number of physical interactions between buses and taxis which can further assist in decision making and could indicate required physical changes in the network which may be required to optimise the system. The analysis indicates that there are different scenarios available in order to achieve different objectives such as improving traffic conditions for general traffic, buses or taxis. The findings also indicate that the current operating conditions (BRT buses have exclusive use of the dedicated lanes) yields the worst traffic conditions for general traffic and minibus taxis. The current scenario also yields the highest overall travel time per passenger. This indicates that consideration should be given to implementing an alternative scenario. The findings (which indicate positive results for shared Right-of-Way) are provisional and require further research. Further research should be focused on expanding on these findings by determining the effects of taxis stopping in BRT lanes as well as safety concerns which are caused by allowing taxis to use BRT lanes. This results in passengers boarding and alighting taxis in BRT lanes (on the moving traffic side of the taxi) and requires specific attention.