As part of a research that led to the development of the performance-based track geometry (PBTG) inspection technology, the Transportation Technology Center, Inc., Pueblo, CO, USA, a wholly owned subsidiary of the Association of American Railroads, has developed a technique relating track geometry to vehicle performance, real-time. This technique is based on the neural network (NN) approach, an emerging powerful tool in recognizing complex patterns and non-linear relationships between many inputs and an output, such as the relationship between track geometry and vehicle response. On the basis of this technique, many NNs have been developed (trained) from actual vehicle/track interaction test results. For a given vehicle type, the trained NNs directly relate three-dimensional track geometry and vehicle operating speed to vehicle performance. The effects of other track conditions such as lubrication, rail profile, and track stiffness are indirectly considered on the basis of their statistical distributions from test results. Because the PBTG inspection is intended to optimize the track geometry maintenance, the vehicle types selected for testing to date were the ones most sensitive to track geometry (in North America, these are the tank car, covered hopper car, and coal gondola car). However, more NNs for other vehicle types can be easily trained on the basis of the NN technique developed using actual vehicle performance and track geometry test results.

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As part of an Association of American Railroads (AAR) research program, the Transportation Technology Center, Inc., a subsidiary of AAR, has developed a new method using its track loading vehicle (TLV) technique to measure vertical track deflections under given vertical loads while in motion. The technique was developed to identify weak track locations and to measure the load-carrying capacity of existing tracks to aid and prioritize track maintenance and to improve railroad operational performance. Discussed are the development and implementation of this continuous vertical track-support measurement technique. This technique provides an in-motion and nondestructive means of testing vertical track support. Currently, this newly developed TLV technique is being used in revenue service to identify large track stiffness variations along the track, indicating lower track strength or abrupt transitional stiffness changes. It is also used to locate the source of lower strength due to ballast and subgrade conditions, as well as to assess the need for upgrades to accommodate higher operation speeds or heavier axle loads. Extensive tests in revenue service have shown this TLV testing technique to be a viable method to perform the above tasks successfully. In addition, this new test technique can be used to improve the understanding of track strength degradation over time and to help direct limited maintenance resources to track locations requiring near-term maintenance.

This article describes the wheel-rail interface management (WRIM) model being developed by Transportation Technology Center Inc. to evaluate wheel-rail interface conditions, plan wheel-rail maintenance, and develop strategies to improve railway system performance. The WRIM software integrates wheel-rail profile measurement data, vehicle performance data, track geometry data, and rail steel properties to predict rail wear and rolling contact fatigue (RCF) based on the shakedown theory, an energy-based RCF damage function, and existing wear rate computation algorithms.

North American railways have experienced significant traffic growth over the past 20 years to the point where many lines are at or near capacity. While the current worldwide recession has eased capacity constraints momentarily, the long-term trends are for continued traffic growth. Faced with the prospects of perhaps doubling freight traffic demand in the next 20 years and adding significant passenger traffic, the railroads are developing cost effective ways to increase capacity. Besides constructing additional tracks, improving the performance (i.e., safety, reliability, and service lives) of key track components is expected. Both heavy axle loads (HAL) and high speed rail (HSR) passenger traffic require high quality, durable track. The paper will describe recent work done to improve the dynamic performance and durability of these track components: • Special trackwork. • Rail joints. • Crossties. • Track transitions. For example, turnouts are being developed that can accommodate freight shippers served from mainline track that also carry high speed traffic. These continuous mainline rail switches and frogs allow slow speed diverging operations that will not affect mainline track performance. The paper will also discuss further heavy haul infrastructure research and development needs.