SAFE BRAKING OF LIGHT RAIL VEHICLES

As Light Rail Vehicles (LRVs) increasingly come under the control of Automatic Train Control Systems (ATCS), there is a need to define the minimum brake rate used to calculate safety distance against which the train control headways must be planned. In order to maximize system throughput, this brake rate must be set as high as feasible, concomitant with safety. This paper demonstrates how the San Francisco Municipal Railway (MUNI) handled the issue, as they simultaneously procured a new LRV fleet, and ATCS. The methods described define a risk-based approach to verify the safety margin of the LRVs operating under a specified guaranteed emergency brake rate (GEBR). The approach uses event tree analysis to postulate all perceivable failure scenarios of the LRV braking systems, and uses fault trees to model the reliability performance of the LRV braking system.