Time-Distance Diagrams: A Powerful Tool for Service Planning and Control

Graphical scheduling is an old technique that has been neglected, or never acquired, in many NorthAmerican transit agencies. It retains its advantages in basic schedule design and analysis as it eases the solution to problems that are difficult to solve analytically. Even information about simple routes is enhanced by the detailed operating characteristics inherent in detailed vehicle trajectories and by the relative ease with which accelerated service and service recovery strategies can be investigated. It also can be used to confirm and refine solutions that are generated by analytic methods. The methodology is reviewed in the context of such planning applications. Graphical scheduling has additional advantages in operational control with the advent of modem ITS technologies. By movement of the cursor on a terminal screen, detailed information about all activity along a route becomes available. It is possible to link the altering of trajectories through clicking and dragging to the automatic issuance of control commands and updates of passenger information. These and other possible uses of the technique in an operational context are presented.