Effect of skip-stop policy on a Korean subway system

An express subway system is planned for the Seoul, Korea, metropolitan area. Many problems are involved in operating an express subway system, such as installation of siding track and scheduling of passing locations and times for different headways. A skip-stop system can be considered as an alternative to express subway service. With a given origin-destination (O-D) demand matrix, distances between stations, headways, and maximum link speeds, the total time saving of a skip-stop schedule that satisfies safety conditions is predicted. In a field study, the time saving effects based on O-D data for Line 5 in Seoul, Korea, were simulated. From the simulation using C language, the peak-hour waiting time increased by 43.8% to 56.3%, but the travel time decreased by 10.8% to 12.9%, compared with the existing system. Waiting time was only 6.9% to 11.6% of the total system travel time-the total system time decreased by 7.1% to 7.8% and, in the maximum case, up to 9.8%. The skip-stop system can be advantageous to the existing system without constructing additional facilities. When the express line is installed, time saving effects and additional construction costs of the three systems (all-stop system, skip-stop system, and express line with siding track) could be compared.