Optimal fleet size, frequencies and vehicle capacities considering peak and off-peak periods in public transport

Document Type

Journal Article

Publication Date


Subject Area

place - urban, mode - bus, operations - capacity, operations - frequency, infrastructure - fleet management, planning - travel demand management, planning - methods


Public transport, Two periods, Optimal frequencies, Optimal bus size


The fleet for surface transit in urban areas - number of buses and vehicle size - is usually determined by the characteristics of demand during the peak period, adjusting frequencies for other periods where those characteristics are quite different. Here the problem is formulated analytically considering a representative single line where hourly passengers flow and average trip lengths differ between peak and off-peak periods. Analytical and numerical results show that minimizing social costs (operators and users) for the whole day yields a larger fleet of smaller buses than if only the peak period is considered. Contrary to previous results on this issue, optimal frequencies across periods differ by a large amount, as optimal peak and off-peak frequencies are larger and smaller respectively than what would be obtained modeling each period by itself. The optimal bus size lies in-between the capacities obtained when each period is independently optimized. Several other interesting counterintuitive results are shown.


Permission to publish the abstract has been given by Elsevier, copyright remains with them.


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