National Academies Press: OpenBook

Center Truck Performance on Low-Floor Light Rail Vehicles (2006)

Chapter: Chapter 1 - Introduction

« Previous: Summary
Page 2
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2006. Center Truck Performance on Low-Floor Light Rail Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/14000.
×
Page 2
Page 3
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2006. Center Truck Performance on Low-Floor Light Rail Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/14000.
×
Page 3
Page 4
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2006. Center Truck Performance on Low-Floor Light Rail Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/14000.
×
Page 4
Page 5
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2006. Center Truck Performance on Low-Floor Light Rail Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/14000.
×
Page 5

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

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

3approximately matches the number of high-floor cars. Figure 1-2 also shows that, within the low-floor sector, the total num- ber of 100-percent low-floor cars matches the total number of partial low-floor cars and that these proportions have changed in the past 10 years.All new orders for light rail vehicles (LRVs) in Europe since 2000 have been low-floor types, except where the systems needed to have high-floor vehicles because they have high platforms. Few European systems have high plat- forms. Given the prevalence and popularity of these designs, solutions to any issues are needed urgently. Chapter 2 of this report discusses low-floor developments and applications in detail. 1.4 Potential Issues The performance issues identified in the research project statement issued by TCRP (1) that have been considered specifically within this study are • Derailments, especially those of the center trucks; • Asymmetric wheel flange wear and grooving of treads; • Excessive rail wear; • Reduced ride quality, including hunting and excessive curving; and • Noise and vibration. These issues will vary with the type of infrastructure (i.e., on different types of embedded and ballasted track, on tan- gent track, curves and special trackwork). Solutions may vary according to this context and all have been considered. The research has been undertaken on the basis that, although sometimes unsatisfactory performance has a single cause, it often has multiple causes. The issues being observed may well be concurrent manifestations of multiple failure phe- nomena and, therefore, even more difficult to isolate and iden- tify. Examples of this would include design issues aggravated by operating practice, infrastructure characteristics, or even something as highly variable as dynamic passenger loading. Chapter 3 discusses performance issues and their possible causes based on the research carried out, which consisted both of original research and reviews of earlier published material on the same topics. Figure 1-1. LFLRV, Santa Clara Valley Transit Authority. Region No. of systems that could use LFLRVs No. of systems using LFLRVs Percentage Application Note USA and Canada 26 8 31% Some old and many new LRT systems UK and Ireland 7 5 71% Mostly new systems France 12 12 100% Some old and many new LRT systems Germany 59 42 71% Many old systems, very few new ones Benelux 9 8 89% Mostly old systems Australia 3 3 100% Mostly old systems LRT, light rail transit. Table 1-1. Examples of the worldwide application of LFLRVs.

41.5 Organization of the Report Chapter 2 describes (1) LFLRV technology and its applica- tion worldwide, (2) how it has developed and the issues that have emerged worldwide, (3) how these issues have been mil- itated against, and (4) how the industry has reacted. Chapter 2 also looks at trends resulting from this experience. Chapter 3 covers each of the identified performance issues. For each issue, generic examples that have occurred in the United States are given with explanations of what type of vehicles and conditions were involved. Chapter 3 also explains potential causes of performance issues, including contribu- tory factors and justifications for the research findings. Chapter 4 is practical guidance on dealing with the per- formance issues, with sections that apply to specific stages in application and to the interests of different users. Chapter 4 includes advice on best practices for system design so as to avoid future issues. Chapter 5 identifies future research that might be carried out either to examine these issues in more detail or to gener- ally facilitate the introduction of LFLRVs in the United States and Canada. Chapter 6 summarizes the conclusions of the research. Appendixes provide more detail on the research carried out, a glossary of the terms used, vehicle data and track data for the systems studied in most detail and a comparison of track maintenance standards between the United States and Germany, and a bibliography. 1.6 Dimensions The U.S. and Canadian transit systems use U.S. system measurements but some of the suppliers will have used the metric system in order to design equipment and products. In addition the research has compared U.S. and European standards where the latter have also used the metric system. The convention that has been adopted in this report is as follows: • U.S. system measurement only—All distances, speeds, mass and weight. Also length, where there is no value in showing a metric equivalent (e.g., the route length of a system). • U.S. system measurements with metric system equiva- lents—Lengths where it is useful to show a metric equiva- lent to facilitate comparison with other metric figures. An example of this would be 3 inches (76.2 mm). • Metric system measurements with U.S. equivalents— Lengths originally specified in the metric system, including manufacturer’s designs and European standards, may also Figure 1-2. Cumulative worldwide pattern of LRV vehicle orders since 1967.

be expressed in the metric system when referred to by some U.S. transit systems. An example of this would be 75 mm (2.95 inches). • Track gauge—This is generally referred to as 1,435 mm, without showing the conversion to U.S. standards (56.5 inches), so as to avoid repetition. Other dimensions associated with track gauge are also shown in millime- ters so as to facilitate comparison. • Fractions—These are used for length dimensions in units of one-half, one-third, one-quarter, one-eighth, and one- sixteenth of an inch; in all other cases, length dimensions are expressed in decimals. 5

Next: Chapter 2 - LFLRV Technology and Applications »
Center Truck Performance on Low-Floor Light Rail Vehicles Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

TRB's Transit Cooperative Research Program (TCRP) Report 114: Center Truck Performance on Low-Floor Light Rail Vehicles examines performance issues observed in the operation of low-floor light rail vehicle (LFLRV) center trucks (focusing on 70-percent low-floor vehicles), such as excessive wheel wear and noise and occasional derailments, and provides proposed guidance on how to minimize or avoid these issues. The report also includes suggestions on LFLRV specifications, maintenance, and design, as well as on related infrastructure design and maintenance, to maximize performance of these LFLRV center trucks.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!