ESTIMATING OPTIMAL TOLLS FOR CROSS HARBOUR TUNNELS IN HONG KONG

This work aims to estimate the distribution of the time-varying toll over 24 hours that minimizes the combined queue length of the three tunnels traversing Hong Kong's Victoria Harbour taking into account institutional constraints. The underlying objective of our time-varying toll scheme is to induce efficient utilization of the total capacities of the three parallel tunnels that traverse the harbour - namely the Cross Harbour Tunnel, the Eastern Harbour Crossing and the Western Harbour Crossing - for each hour, while exacting the lowest toll fee from motorists. The approach follows William Vickrey's basic idea of equating effective demand with the space available at congested toll facilities (Vickrey, 1967, 1996). A simple model is developed to analyze the traffic flow between Hong Kong Island and the Kowloon Peninsula (May and Keller, 1967). The origin-destination matrices are obtained from the year 2002 daily matrices, and are divided into 24 hourly matrices based on the Travel Characteristics Survey. For a particular hour, each origin-destination pair and each vehicle class, the proportions of flows passing through a particular harbour crossing are determined by a multinomial logit model of the standard form (McFadden, 1974). The utility coefficients are estimated from stated preference survey data in which 465 persons were interviewed with five hypothetical scenarios involving three variables of toll fee, queue length and alternative-specific dummy posed in each interview.