Effects of Line-Capacity Reductions on Urban Rail Transit System Service Performance

Abstract

In the daily operations of urban rail transit (URT) systems, line capacity sometimes is reduced, which worsens service performance. To measure the effects of line capacity reductions on URT system service performance in a given period, a passenger satisfaction metric and a service quality metric are proposed. The passengers’ generalized travel cost (GTC) is the sum of the monetary value of perceived travel time and travel fare, because perceived travel time can reflect the value of the seat availability and transfer times. When line capacity is reduced, passengers are divided into three categories. Passengers in Categories 1 and 2 still can travel on URT, whereas passengers in Category 3 cannot, due to insufficient capacities on their paths. During reductions in line capacity, the relative GTC stays below a fixed GTC threshold for passengers in Category 1, and above it for passengers in Category 2. Passengers in Category 1 receive acceptable service because their GTC increases only slightly. The fraction of passengers in Category 1 and the average GTC per passenger in Categories 1 and 2 in a given period are defined as passenger satisfaction and service quality metrics, respectively. The system service performance in Wuhan, China’s URT during morning peak periods and the effect of providing discount fares on system service performance were computed for separate capacity reductions in each rail line. The results show that the proposed indicators and methods can identify the critical lines that greatly affect URT system service performance. The proposed indicators also can identify the number of lines with reduced capacity and the capacity reduction ratios that a URT system can withstand while maintaining particular system service levels. Providing discount fares is an effective way to improve URT system service performance when a line’s capacity is reduced slightly.