Speed choice behaviour-based methodology for evaluating the effects of pavement roughness on travel time cost and discomfort cost

Evaluating the effects of pavement roughness on the travel time cost (TTC) and the discomfort cost (DCC) is essential for user cost estimation in road maintenance planning and for benefit assessment of investments on maintenance. However, existing related studies are quite limited. The main obstacles are the lack of well-defined mechanisms to (i) understand the riders' speed choice behaviour and (ii) quantify the riding discomfort cost. To narrow this gap, a new method is developed in this study to evaluate the incremental TTC and DCC caused by roughness increasing. By representing the ride quality and the roughness with 'jolt' and the international roughness index (IRI), respectively, a ride quality indifference curve (RQIC) is developed. Then, using the RQIC and the traffic flow fundamental diagrams before and after an IRI increase, the riders' speed choice behaviour is modelled. The selected speed after the IRI change is explained as the balancing result between efficiency and comfort that satisfies the proposed marginal principle. Applying this principle, the procedures to calculate the TTC and DCC increments are designed. Finally, a application example of the method is presented. The method proposed herein mainly contributes to the user cost estimation in the post-evaluation of the road maintenance.