Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation (2010)

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S U M M A R Y 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. Guard/Restraining Rail Study—Phase II 1

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.