Joint optimization of bus size, headway, and slack time for efficient timed transfer

The level of transit service may be elevated by efficient timed transfer, which reduces travel time and increases productivity. However, timed transfer may be costly because of the stochastic nature of vehicle arrivals. A mathematical model is developed to minimize the total cost (e.g., operator and user costs) of a transfer hub that consists of multiple transit routes, subject to capacity constraints. The decision variables, including bus size, headway, and slack time, are jointly optimized through consideration of various levels of coordination. A numerical example is given to demonstrate the applicability of the developed model.