  The paper introduces and evaluates the concept of the dynamic interlining of
buses. Dynamic interlining is an operational strategy for routes that have a
terminal station at a common hub, that allows a portion of (or all) the fleet
to be shared among the routes belonging to the hub (shared fleet) as needed.
The shared fleet is dispatched on an on-demand basis to serve scheduled trips
on any route to avoid delays and regulate services. The paper examines
systematically the impacts of dynamic interlining on service reliability. It
formulates the dispatching problem as an optimization problem and uses
simulation to evaluate the dynamic interlining strategy under a variety of
operating conditions. Using bus routes in Boston Massachusetts Bay
Transportation Authority (MBTA) as a case study, the feasibility of the
strategy, as well as factors that affect its performance are investigated.
Results show that dynamic interlining can improve service reliability
(increases on-time departures and decreases departure headways variability at
the hub). The fraction of the fleet that is shared has the most dominant impact
on performance. In the case where all buses are dynamically interlined, the
performance improves as route frequency increases and more routes participate
in the strategy.
