Vehicle Pooling in Transit Operations

The benefits of pooling vehicles among routes that emanate from a common focus terminal are examined. In this strategy, trips are still scheduled, but vehicles are not assigned to specific trips. Instead, vehicles belonging to the pool serve all of the round trips leaving that terminal in a first in/first out sequence. Pooling improves schedule adherence, since in a pooled system a bus returning early can “cover” for a bus returning late. Pooling also facilitates interlining (sharing of buses among routes), which reduces the need for slack time. A procedure is developed for estimating schedule reliability. This procedure is applied to a set of 8 routes emanating from a Boston area terminal where it was found that with pooling the fleet size could be reduced by 11% while at the same time improving schedule adherence.