Schedule Adherence Support


Schedule adherence applications provide information and tools to assist dispatchers to keep the service operating to schedule. The approach can be somewhat different depending on whether the service is operated to schedule/timetable, or to planned headways. Schedule adherence applications are invariably implemented within CAD/AVM systems.

Schedule adherence applications can be split among:

  • the CAD/AVM Control Centre, where the Dispatcher uses the information to determine the interventions required to improve schedule adherence (considered here)
  • the vehicle, where schedule and relative headway information is provided to the driver, assisting him/her to manage schedule adherence on the road (considered below)
  • the traffic priority system, which can grant priority to vehicles on-schedule or in delay, but not to vehicles running early, to reduce the risk of bunching (considered below)
  • the planning function, which uses information from the CAD/AVM system to identify where the schedule may need to be adjusted to optimise schedule adherence (considered below)

The basic tools for schedule adherence are Computer-Aided Dispatch and Route Condition Monitoring. The dispatcher uses the information and tools available from these applications to make decisions on how to manage the service, and to get vehicles to depart on time or according to headway specification.

Three additional software facilities can provide further assistance for Schedule Adherence:

  • Highlight delays and excessive intervals, so that the dispatcher focuses on these items
  • Predict and highlight to the dispatcher any vehicles that will arrive at the terminal point too late to commence their next trip on time. This uses a combination of current location, current delay status, and known sectional running times. This gives the dispatcher advance warning of delay events, allowing him/her to plan mitigating actions.
  • Predict and highlight to the dispatcher any vehicles that are likely to be in delay for a scheduled crew change or meal break, and thus cause cascading delays in services. This gives the dispatcher the opportunity to prioritise such vehicles for intervention, so that the change-over or meal-break happens on time.

Technologies, data and resources

Schedule Adherence Support is a software application, normally performed on the CAD/AVM server.

It utilises three primary data sources:

  • Real-time vehicle location
  • Predicted vehicle location and arrival times at terminals
  • (Semi-) fixed route information, including route map, schedules, intermediate travel times, meal breaks and change-over times and points

Advantages and Cautions

The primary advantages of Schedule Adherence Support are to:

  • ensure that emerging problems are identified while there is still time to mitigate them
  • avoid cascading impacts on subsequent trips
  • achieve good schedule adherence without excessive intervention

The principal cautions are similar to those for CAD/AVM:

  • comprehensive operations management procedures must be in place. It is not sufficient to display the information. It must be understood and acted upon.
  • dispatchers might focus excessively on ensuring that meal breaks and crew change-overs happen on time (i.e. keep the drivers happy), and make excessive interventions that are inconvenient to customers or that lose part-trips unnecessarily

Relevant Case Studies

Florence, Zurich