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1 SUMMARY Guard/Restraining Rail Study--Phase II This report compares the effects of two guard rail installation philosophies on transit vehicle wheel/rail (W/R) force, wear, rolling resistance, and axle steering capability. The effects of vehicle types, wheel flange angle, W/R friction coefficient, curve radius, cant deficiency, and track perturbation on flange climb derailments were also investigated through NUCARS simulations. A number of conclusions regarding guard/restraining rail installation in terms of vehicle type and track geometry are drawn from this work including the following: Philosophy I (shared contact between the high-rail flange and the guard rail on the low-rail wheel) leads to better vehicle dynamic performance than Philosophy II (no high-rail flange contact and with the guard rail contact on the low-rail wheel) in terms of lower lateral forces on rails, lower vehicle rolling resistance, and lower leading axle wear. Both philosophies lead to higher vehicle rolling resistance and leading axle wheel wear compared with the case with no guard rail. The axle steering capability difference between these two philosophies is negligible. The Nadal limit and the flange climb distance limit are the criteria for flange climb derailment; they are adopted as the guard rail installation criteria in this report. There are many factors leading to flange climb derailment. Three factors have the most critical effects: wheel flange angle, W/R friction coefficient, and track perturbation amplitude. Flange climb derailment risk decreases as wheel flange angle increases: the larger the wheel flange angle, the smaller the guarded curve radius. Flange climb derailment risk decreases as W/R friction coefficient decreases: the lower the friction coefficient, the smaller the guarded curve radius. No guard rail is needed for all sim- ulated vehicles if the friction coefficient can be kept under 0.4. Flange climb derailment risk increases as track perturbation increases: the smaller the track perturbation amplitude, the smaller the guarded curve radius. Transportation Technology Center, Inc., (TTCI) recommends the adoption of 75 flange angle wheels for both transit cars (Types 1 and 2) and light rail vehicles (Types 1 and 2) to prevent flange climb derailment. From a safety point of view, the guard rail installation guidelines for the simulated transit rail cars (Types 1 and 2) and the light rail vehicles (Types 1 and 2) (defined in Table 2 of this report) with the recommended 75 flange angle wheels are the following: For yard curves (15 mph speed limit) with the most severe (Level 3, shown in Figure 21) track perturbations: No guard rails are needed for Type 1 and Type 2 transit rail cars or Type 2 light rail vehicles. Guard rails should be installed on curves with radii less than or equal to 755 ft for the Type 1 light rail vehicle.

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2 For main-line curves: No guard rails are needed for Type 1 and 2 transit rail cars running at a 7.5 in. cant deficiency speed with Level 2 (shown in Figure 20) track perturbations. No guard rails are needed for Type 1 light rail vehicles running at a 7.5 in. cant deficiency speed with Level 1 (shown in Figure 19 in the report) track perturbations. No guard rails are needed for Type 2 light rail vehicles running at a 4.0 in. cant deficiency speed with Level 1 track perturbations. Guard rails should be installed on curves with radii less than or equal to 500 ft for Type 1 light rail vehicles running at a 4 in. cant deficiency speed with Level 2 track perturbations. Guard rails should be installed on curves with radii greater than or equal to 955 ft for Type 2 light rail vehicles running at a 4 in. cant deficiency speed with Level 2 track perturbations. Vehicle curving performance is different from case-to-case due to many factors stemming from vehicle and track aspects. The guidelines listed here as well as the details provided in Tables 7 through 10 of the report could be used as a reference and applied by taking into account the specific vehicle/track features and operating environment. These guard rail installation guidelines do not apply to special trackwork, such as the guard rails for switches, crossings, and turnouts.