Citation

Romedy L. IMSA J. 2000; 38(6): 44-45.

Copyright

(Copyright © 2000, International Municipal Signal Association)

DOI

unavailable

PMID

unavailable

Abstract

In Jacksonville, Florida, when the Florida East Coat Railway rebuilt a railroad crossing which intersected two streets in close proximity, separate preemption signals were provided for each crossing. It was determined that four different preemption sequences would be needed to control the rebuilt crossings. The standard NEMA and 170 controller internal preemption logic which had controlled the original railroad crossings was unable to properly control the newly designed intersections. Relay circuitry was designed to provide the preemption sequence priority selection external to the existing 170 controller. The relay interface panel was made up of two banks, or sets, of three relays each. Each railroad preemption call relay bank was composed of a railroad preemption call relay, a preempt sequence selector relay, and a latch relay. They control the incoming preempt call and provide sequence priority selections to one of four independent preemption logic sequences supplied by a standard NEMA 8-phase controller. The relay panel's operation has remained trouble free since its December 1998 installation.