Keeping Your Passengers on the Rail
Strategies for Preventing Derailments
4. The subject of friction at the wheel/rail interface was briefly discussed earlier in this article. Indeed, friction management is a topic worthy of several articles on its own. A sound program established to address rail wear and friction throughout an operation — either through track-based systems, vehicle-based mechanisms or a combination of both — can be a critical element of a successful derailment prevention strategy.
5. In addition to being aggressive about performing maintenance on track infrastructure upon awareness of issues, additional steps can be taken with the right-of-way that can provide additional protection against derailments:
A) Limit warp to no more than one inch in 10 feet (or less depending on axle spacing associated with the vehicles on the system) and no more than two inches in 60 feet (truck center spacing) to protect against wheel unloading.
B) Install guard rail on sharp curves to avoid wheel climb. Guard rail can also reduce the gage wear of high rail. In general, the guard rails are installed inside of the low rail. For very sharp curves, it is recommended to install guard rails on both the inside and outside rails.
6. The characteristics of a vehicle’s suspension system are critical to its susceptibility to wheel unloading and derailment. A soft primary suspension will provide better steering of the truck over curved track, hence reducing applied lateral forces on the track that cause derailment. However, the use of very soft primary suspension may affect the vehicle’s lateral stability. Optimized characteristics of the primary suspension may be required in case of high-speed trains.
7. Perhaps the most important component of a derailment prevention strategy is the proper attention to VTI management. This is a subject that should concern both track and vehicle maintainers, but overall responsibility is often an issue. In most cases, it’s split between track and vehicle maintenance and operations. Regardless of who is responsible, it is extremely important that someone in the operations “own” the responsibility for VTI-related issues.
Brian Whitten is a senior staff engineer and manager of high speed rail programs with Ensco. Eric Sherrock is a staff engineer and serves as the program manager for Ensco’s operations, maintenance instrumentation and analysis support contract for the Federal Railroad Administration’s Office of Research and Development. Dr. Khaled Zaazaa, a staff engineer with Ensco, is the co-author of the book Railroad Vehicle Dynamics – A Computational Approach. After 33 years as an active member of the rail safety and R&D communities with Ensco, Kevin Kesler left in September to launch NexRail LLC.
