EVALUATION OF RAILROAD PREEMPTION CAPABILITIES OF TRAFFIC SIGNAL CONTROLLERS

The subject of railroad preemption has historically not received much attention in professional literature. All aspects of preemption need to be studied and reported on in greater detail. This research examined and compared the preemption capabilities of a number of currently marketed actuated traffic signal controllers based on the Naitonal Electrical Manufacturers Association standard. Shortcomings in their preemption logic were identified, and preemption issues were discussed in terms of their operations. The evaluation was conducted from a pragmatic point of view to determine whether modern controllers allow practical and reasonable preemption design in conformance with accepted traffic engineering practice. Recommendations are offered with respect to minimum desirable operational capabilities, as well as railroad preemption nomenclature and user documentation.