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2 CHAPTER 1 Introduction 1.1 Background and Research less than that of the conventional motored trucks at the outer Objectives ends of the vehicle. The research was commissioned in order to better under- The purpose of this research was to help introduce low- stand the performance of these center trucks, to compile les- floor light rail vehicles (LFLRVs) into the United States sons learned to date, and to provide guidance to transit and Canada. LFLRVs offer significant advantages, espe- agencies and LFLRV manufacturers in mitigating issues with cially in terms of easier accessibility and the ability to use less- this type of vehicle. This report concentrates on these objec- intrusive low platforms at stops. LFLRVs are especially tives and provides the associated guidance. attractive for new systems and have become the "standard" design solution offered by all the major suppliers. Unfortunately, some LFLRVs that use unpowered wheels 1.2 Research Activity on stub axles on the articulated center section experience The research contract was conducted by Interfleet Inc. who issues with excessive wheel wear and derailments. Vehicles of formed a team that as well as their own experts in this field, this type operate in transit systems in several cities in the included researchers from the following firms: United States, Europe, and Australia--some for more than a decade--and the success of these vehicles has varied. · Raul V. Bravo and Associates; The typical design for a 70-percent low-floor vehicle on a · ZETA-TECH Associates; U.S. light rail transit system comprises a three-section articu- · PROSE AG (Switzerland); lated vehicle body with the center section mounted on a truck · Transport Technologie Consult Karlsruhe (TTK) (Ger- with non-powered, independently rotating wheels. The lead- many); and ing and trailing sections of the vehicle are each supported by · Institut für Bahntechnik (IFB) (Germany). a motored truck at one end and by the common non-powered center truck, via the articulation, at the other. The low-floor Appendix A describes the activities carried out. height precludes the use of conventional wheel sets with solid axle connections between right and left wheels of the center 1.3 Worldwide LFLRV truck. Figure 1-1 shows a vehicle of this type used at Santa Developments Clara Valley Transit Association (VTA) in Santa Clara, California. To date, LFLRVs have been introduced in eight U.S. tran- Unlike a conventional wheelset, the independently rotating sit systems. Given that roughly 22 systems in the United wheels (IRWs) of such a center truck cannot steer the States and 4 in Canada might use them, this means that 31 per- wheelset through the curve. This inability leads to increased cent of systems have applied this solution. Table 1-1 compares flange wear, gauge face wear, stick/slip noise, and the poten- these figures for the United States and Canada and other tial for derailment at curves and on lateral discontinuities in parts of the world. This table suggests that in the United alignment. External factors related to the configuration of the States use of this technical solution is more cautious than overall vehicle design have a stronger influence on the other countries. dynamics of the truck than with conventional running gear. Figure 1-2 shows the cumulative supply of light rail vehicles Wheel life of the low-floor center truck can be significantly worldwide since 1967. The numbers of low-floor cars now