Train control for light rail systems on shared tracks

New Jersey Transit (NJT) will install a light rail system along the Delaware River connecting the cities of Camden and Trenton. Light rail vehicles (LRV) will share Conrail freight trackage through 85% of the 34 mile long route; this will be one of the few freight and light rail shared traffic lines in North America. The train control system for the Southern New Jersey Light Rail Transit System (SNJLRTS) will be used by both LRT and Conrail freight trains. Significant differences in operating characteristics of light rail vehicles and freight trains, such as maximum allowed speed, length and weight of the consist, and brake rate, constitute technical problems that require unique solutions to assure effective and safe traffic for both types of vehicles. The SNJLRTS will employ a relatively simple signaling system that includes three-aspect automatic block signaling and automatic trip stops at the signals with red aspects. Block signal design will be one of the major issues associated with mixed traffic. The rules for conventional block signal design will be only partially applicable for SNJLRTS. In order to comply with internal NJT practices and Federal Railroad Administration (FRA) rules, and at the same time fulfil contract specifications requirements, unique solutions must be found for certain block signal design elements. The logic of grade crossing warning functioning will be another critical issue for mixed traffic. This paper describes the technical solutions that reconcile the LRT and freight train operational differences while designing the SNJLRTS train control system.