Wheel-squeal mitigation measures implemented on the
Mission Valley West extension of the light rail transit system of San Diego, USA

Reprinted from Rail Engineering International
Edition 1999 Volume 28 Number 4

On 23 November 1997, San Diego Trolley Inc. (SDTI) started revenue services on the 6.1 mile-long (9.7 km) Mission Valley West extension of its light rail transit system (Fig. 1). Soon afterwards, it became apparent that nearby residences and businesses experienced noise caused by the wheels of the light rail vehicles (LRVs) rolling over the new rails, which featured scale and pitting as a result of rolling during their manufacture. In December 1997, rail grinding was carried out to alleviate the problem.

However, shortly afterwards, the Metropolitan Transit Development Board (MTDB) of San Diego and SDTI again started to receive complaints from nearby residents. This time it concerned noise caused by squealing of the wheels of the LRVs. Resolved to reduce and, hopefully, to eliminate this problem, MTDB and SDTI diligently set out to address it.

First, a study was carried out to locate the noise areas on the line, It was found that wheel squeal was produces on curves featuring a radius of less than 1200 feet (365 m) and a grade of 3% or more, an on a rigid track (concrete sleepers and direct fixation)

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Light Rail Transit Noise Control:  A New Line For Tri-Met

Article By:  Ken Kirse and Lisa Cobb
Tri-County Metropolitan Transportation District of Oregon (Tri-Met), Portland, OR

(Excerpt from Full Article)  About the same time, Tri-Met learned that San Diego Trolley was successful in eliminating wheel squeal by using wayside rail lubricators. After a trip to San Diego to observe their lubrication practices, Tri-Met is in the process of procuring three similar wayside lubricators. The objective is to reduce the top rail coefficient of friction to a range of .25 to .35. Friction below this level will present braking and acceleration problems. Friction about this level correlates with wheel squeal. Tri-Met chose an electric wayside lubricator so that a precise amount of lubricant can be applied to the passing wheels. The lubricant is Teflon based, non-toxic, biodegradable, and non-polluting. The intention is to cover several noise-producing curves with on lubricator. San Diego has found that the lubricant will track for several miles. After installation of the lubricators, Tri-Met will be conducting braking and acceleration tests.

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