Tracking the Performance of Heavy Axle Load Vehicles in Revenue Service

Abstract

As market forces drive up the gross weight on rail, railroads continue moving toward increased usage of heavy axle load (HAL) equipment, namely 286,000 lb and 315,000 lb GWR vehicles that provide more competitive and efficient transportation. According to the AAR's Universal Machine Language Equipment Register (UMLER) database, since 1995, at least 70% of vehicles built each year were HAL vehicles. 2005 had 49,923 more HAL vehicles running on the North America railroad system than the previous year. This practice can result in significant overall savings in operating costs. However, HAL equipment can also accelerate wear and damage to the railroad infrastructure and have a greater potential for truck warping and vehicle dynamics problems. Thus, keeping rolling stock and track safe while ramping up the usage of HAL equipment presents a significant challenge. Wheel Impact Load Detector (WILD) SuperSites, developed by Salient Systems Inc. (SSI), provide real time monitoring and alarming on excessive axle loads and vehicle dynamics. SuperSites are important tools in the scientific study of HAL vehicles and the monitoring of heavy haul operations. This paper provides a snapshot of results of studies conducted on Union Pacific (UP) HAL routes and demonstrates how HAL loads affect the rolling stock, the track, and the wheel/rail interaction. The heavier the load, the higher the impact of the defective wheels to the track; therefore, heavily loaded vehicle routes (such as the coal route from the Powder River Basin to Kansas City and the primary intermodal route from Los Angeles to El Paso) need to be monitored more proactively to avoid track structural damage.

Quantification of rail transit wheel loads and development of improved dynamic and impact loading factors for design

“…A WILD consists of rail-mounted strain gauges installed over a series of ballast cribs that are oriented in a manner that captures vertical rail strain which can be related to wheel loads 4,7 (Figure 2). A typical WILD site is over 15 meters (50 feet) in length, with cribs instrumented at various intervals to capture a single wheel's rotation five times, recording peak impact and average forces at a data collection rate of up to 25,000 hertz (Hz).…”

“…For the heavy axle load (HAL) freight railroad operating environment, research has been conducted to quantify the load at the wheel-rail interface. [4][5][6][7] To date, there has been comparatively little work conducted on rail transit systems, although commuter rail systems have been studied when their rolling stock operates on infrastructure owned by freight or intercity passenger rail operators. 8 It is hypothesized that the health of wheels found on rail transit rolling stock is quite good, due to more frequent wheel trueing and other forms of vehicle and track maintenance; thus, they likely generate lower dynamic and impact loads.…”

Condition Monitoring of Rail Transport Systems: A Bibliometric Performance Analysis and Systematic Literature Review

“…This system collected monitoring data in order to detect potential defects in wheels based on the measurements of at least one strain sensor , with the ability to monitor more features of the wheel condition using the same system. This system was also used by other researchers, as in Gao et al and Harrison et al [ 146 , 316 ], for more complex solutions.…”

Quantification of Loading Environment and Flexural Demand of Prestressed Concrete Crossties under Shared Corridor Operating Conditions

“…A WILD is an electronic data collection device designed to measure and isolate vertical and lateral wheel forces with the use of either rail mounted strain gauges or accelerometers ( 8, 9 ). Although its primary objective is to evaluate the performance of the rolling stock and measure the impact forces caused by out-of-round or otherwise damaged wheels ( 9, 10 ), it has also proven to be a practical mechanism for producing reliable wheel load data that can serve rail infrastructure researchers and practitioners ( 2 ).…”