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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
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3In 2005, Transportation Technology Center, Inc. (TTCI) conducted research for TCRP Project D-7/Task 12, “Guard/ Restraining Rail Study” to develop guidelines for the application of guard/restraining rails in transit systems. TCRP Research Results Digest 82: Use of Guard/Girder/ Restraining Rails was published in 2007 (1) as a result of this study, and it recommended simultaneous contact between the guard and high rails, which would result in the sharing of lateral forces. The optimal flangeway clearances needed to achieve this were included in the report. A general guideline based on a wheel lateral-to-vertical force (L/V) ratio and flange climb distance criteria was also proposed. Subsequently, TRB Committee AP080, Rail Transit Systems Design, suggested that the two guard rail installation philosophies described in the following sections be compared. 1.1 Philosophy I The “shared contact” methodology will be referred to as guard rail installation Philosophy I (illustrated in Figure 1). The optimization methodology proposed in the previous study (1) for optimal flangeway clearance clearly belongs to Philosophy I. With equal rates of wear, it is expected that the high rail and the guard/girder/restraining rail will wear out at the same time and be replaced during the same track mainte- nance period, minimizing service interruptions. 1.2 Philosophy II There is a different guard rail installation philosophy used by transit systems that will be referred to as Philosophy II (illustrated in Figure 2). The methodology of Philosophy II is to increase the check gage dimension and track gage so that no flange contact with the high rail will occur under any com- bination of wear and tolerances. As a result, the guard/girder/ restraining rail resists all the curving forces and therefore experiences all the gage face wear, while the high rail experiences only rail head wear. Philosophy II can be accomplished by simply widening the track gage. The following (based on the Research Needs Statement for Optimizing the Check Gauge of Restraining Guard Rail1) are reasons for installing guard rails using Philosophy II: • Because of the variations in the wheel mounting back-to- back dimensions, wheel flange wear, rail gage face wear, and track gage variations, it is impossible to have shared contact with both the high rail and the guard/restraining rail in any reliable manner. This can result in contact that is shared intermittently, and adverse steering forces are introduced into the trucks, resulting in rapid oscillation and in signif- icantly increased nosing forces. These forces can damage the track, such as gouging wear of both the high rail and the guard/restraining rail and breaking the bolts holding the guard/restraining rail. The sudden, adverse steering forces also are likely to result in a lurching and an uncomfortable ride in the vehicles, especially for standing passengers. • Contacting the back of the flange on only the guard/ restraining rail reduces curving noise, since only one rail and one wheel are involved as opposed to two. This results in less bell-ringing and wheel squeal and significantly reduces wear on the high rail so that the high rail has a considerably extended life, roughly equal to that of the low rail. Even though the wheel/rail (W/R) contact of these two philosophies starts in two significantly different situations, they ultimately end with the same situation as Philosophy I, because the high-rail contact will eventually occur for Philosophy II as the guard/restraining rail gradually wears in. The obvious question is this: Is Philosophy I or II the cor- rect way of installing a guard rail? It is an important question because it could lead to operating safety issues, premature C H A P T E R 1 Introduction 1 Research Needs Statements: Optimizing the Check Gauge of Restraining Guard Rail, http://rns.trb.org/dproject.asp?n=13826.

wear, or damage to the track that increases the maintenance requirements, poor ride quality, and additional noise. Consequently, in 2008, TTCI conducted research for TCRP under TCRP Project D-07/Task 16, “Guard/Restraining Rail Study—Phase II” with the following three tasks: • Task 1: Conduct a literature review of guard/restraining rail installation guidelines and the philosophies behind them. • Task 2: Quantify the performance/benefits of both philoso- phies and recommend a preferred method through model- ing using the following key results as a basis for comparison: – Lateral forces developed (implying damage on rail and fastening system); – Rolling resistance (implying energy consumption); – Wear index (including wear of both the flange face and flange back); and – Axle angle-of-attack (implying axle steering capability). • Task 3: Develop guard rail installation guidelines based on track curvature, vehicle type, and operation condition. This report presents the results of the work done in support of these three tasks. 4 Low Rail High Rail Figure 1. Guard rail installation Philosophy I. Low Rail High Rail Figure 2. Guard rail installation Philosophy II.

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TRB’s Transit Cooperative Research Program (TCRP) Report 71, Volume 7: Guidelines for Guard/Restraining Rail Installation explores two guard rail installation philosophies and the effects of vehicle types, wheel flange angle, wheel/rail friction coefficient, curve radius, cant deficiency, and track perturbation on flange climb derailments.

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