On Travel Time Functions for Mixed Traffic Systems Dominated by Motorcycles

Abstract

Mixed traffic systems dominated by motorcycles (MTSDM) are characteristic for developing countries like Taiwan, Vietnam, The Philippines, Thailand, or India. The present paper investigates a new travel time function including not only the driving time but also the waiting time at the signal line on a link in such a traffic environment. Foremost, a review of popular travel time functions with discussion about their advantages as well as disadvantages when applied in a traffic assignment (TA) model is discussed. Suitable parameters for applying the Bureau of Public Road (BPR) function to an MTSDM are calibrated after introducing a method to estimate the practical capacity of a link based on the certain saturation flow. The travel times calculated by the new BPR function turned out to be highly accurate when compared to the simulated travel time in VISSIM---a popular traffic visualization software. Moreover, the User Equilibrium (UE) model using the new function could forecast traffic flows close to the real flows collected in Hanoi,Vietnam.