Maximizing number of direct trips for a skip-stop policy in metro systems

Despite multiple benefits, a few metro systems around the world operate a skip-stop policy. The benefits include accelerating service, reducing passenger travel time, and enhancing economic performance. However, skip-stop polices may force many passengers to conduct indirect trips (using more than one train), which is a major source of inconvenience to passengers. This paper constructs a binary quadratic programming model to maximize the number of direct trips in a single one-way double-track metro line. The model produces the optimal skip/stop arrangement of stations while assuming three known scenarios of arranging stations. The model is linearized, validated by exhaustive enumeration, and solved for two sets of examples of size 20 stations. The number of skipped stations is varied to obtain the best compromise between the percent saving in travel time and the percent decrease in the direct trips. As compared to all-stop policy, results show that 16% saving in travel time can be achieved while sacrificing only 11% of direct trips. The model provides the metro line operator with alternative arrangements of stations that offer nearly the same measures of performance.