Modal Shift of Car Travelers to Buses Based on Bus Priority

One of the most significant measures of alleviating urban traffic congestion are the bus priority policies. However, for the implementation of bus priority measures, the deviation on estimating traffic flow assignment to bus lanes and general lanes may lead to the waste of road space resources, and consequently fail to achieve the purpose of bus priority. To describe the rational traffic assignment, this paper presents a modal shift relationship between buses and private cars based on road impedance function. Two types of lanes, bus lanes and general lanes are discussed in association with their specific impedance functions. Obviously, the average passenger volume of a bus (60 passengers per vehicle in this paper) is larger than a private car (2 passengers per vehicle), therefore, due to conditions of invariant total passenger trip volume, modal shift between the two traffic modes will influence the traffic volume of the road. A combined model combining bus proportion and impedance function was developed, and travel speed curves of buses and cars under various bus proportion were described. The result shows that in accordance with specific passenger trip volume, there will be an ideal bus proportion in which car travelers are willing to shift to buses, and road traffic systems will be optimized as well.