Design differences in light rail systems are primarily related to their operating environments. Since the latter can vary over a large range, the appropriate level of signal automation varies by transit agency, their operating requirements for speed and headways, and the configuration and alignment of the track system components, including special trackwork. These can vary significantly along a given LRT line. It is not uncommon for an LRT line to be very much like a streetcar along one segment of its route, but have a semi-exclusive or completely exclusive trackway only a short distance further down the track. The optimum level of signal sophistication depends on such local circumstances and is generally determined by the transit agency responsible for providing the service.
While these issues have relatively little effect on trackwork, they have a significant effect on track alignment. Specifically, where the maximum diverging speed over turnouts or civil speed restrictions are enforced by the train control system, there are a limited number of speeds that can be enforced by the cab signal codes. The actual speed assigned to each code can vary from property to property, and a decision needs to be made early on in the track design as to what the enforced speeds should be. It does little good to design a curve to accommodate a civil speed limit of 70 km/jam if the available speed commands are 50 and 80 km/jam. Since the curve isn’t good for 50 mph, it would be restricted to 30 mph by the train control system.
