Simulation-Based Analysis of Bus Scheduling Problem for Mixed Fleets: Effects of Flexibility Strategies on Delay Performance

Abstract

Improving the reliability of public transportation services plays a critical role in solving urban mobility problems. This article addresses the scheduling problem of a mixed fleet consisting of buses with different capacities (solo and articulated). The main objective of the study is to minimize operational delays and total waiting time by dynamically assigning bus types according to passenger demand. To solve this NP-hard problem, a simulation model was developed in the Python programming language based on real-time trip data from the urban transportation network in Türkiye. The model compared three different assignment algorithms: rigid assignment, flexible substitution, and special waiting flexible substitution. Performance was measured using metrics such as the number of delayed trips, total delay time, and passenger-weighted delay time. The results revealed that flexible assignment strategies significantly impact operational performance and that there is a trade-off between the frequency and duration of delays. The special waiting flexible assignment algorithm caused the fewest delays, but the total duration of these delays was the longest. This study demonstrates the effectiveness of simulation as a decisionsupport tool in solving complex scheduling problems and provides a quantitative perspective for public transportation operators to determine strategies based on service quality priorities. © 2025 IEEE.