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5A guard/restraining rail practice survey was conducted during the Phase I study (1) and during TCRP Project D-07/ Task 8 published as TCRP Report 71, Volume 5: Flange Climb Derailment Criteria and Wheel/Rail Profile Management and Maintenance Guidelines for Transit Operations (2). Radii of curves on which transit systems install guard rails differ from 500 to 1,000 ft. The flangeway clearance differs from 1.5 to 2.5 in. depending on the wheelset and track geometry dimensions. Most of the track standards used on various transit properties are based simply on prior practice without independent verification that the practice is still appropriate or effective. The Phase I study proposed optimization methodologies for guard rail installation based on the âsharing contactâ philos- ophy (Philosophy I), which need to be justified. This study conducted an additional literature review that focused on the guard rail installation criteria or standards worldwide and the philosophies behind them. However, there is very little liter- ature published on these topics. The following comments are based on the results of the literature review. One of the main functions of a guard rail is to prevent flange climb derailment. Most flange climb derailments occur under the following conditions: ⢠Tight curves or small radius switches, mostly in yards; ⢠Low flange angle wheels; ⢠High W/R friction coefficient, such as a new trued wheel with a rough surface; ⢠Independent rotating wheels (IRW); and ⢠Severe track perturbations. Table 1 shows that the wheel flange angle used in different transit systems ranges from 63 to 77° (3). The effect of the flange angle and the other factors listed above, including vehicle suspensions and the operation environment, on flange climb derailment needs to be investigated in order to create guard/ restraining rail guidelines. C H A P T E R 2 Literature Review Wheel Flange Angle Transit System* 63° BART (Transit Rail Car), Toronto, SEPTA, WMATA (Transit Rail Car) 70° Santa Clara VTA, Portland MAX, Edmonton, Houston, Baltimore, Dallas, KOLN, SEPTA (Transit Rail Car) 75° MBTA, NJT HBL and Newark, San Diego, Pittsburgh 77° BOCHUM, ZURICH * The vehicles in this table are Light Rail Vehicles (3), except for those specified as Transit Rail Car. Table 1. Wheel flange angle.
