Click for next page ( 48


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 47
47 an indication of how tight they may need to be, but each system the choice depends on local circumstances. For an entirely should derive tolerances for its own conditions. This is not a list new system, the choice of LFLRV and guidelines to be fol- of all the features that should be included, but concentrates on lowed will be influenced by the type of system. It is not nec- those features especially important for operating the type of essary to have an "optimum" solution that will suit any type LFLRV being studied. These are derived from the guidelines of system--doing this may add unnecessary cost and inflexi- mentioned in Sections 4.9.2 through 4.9.5. Where actual toler- bility to new transit networks. ances are shown, these will only apply to vehicles that also con- The next fundamental issue is the choice of floor height. In form to the guidelines for new track specified in those sections. the future, most entirely new transit systems may want to use The researchers assume that the basis for the system's mainte- low-floor vehicles in order to meet ADA requirements. An nance standards are APTA's Standard for Rail Transit Track exception may be Type 2 systems that might economically use Inspection and Maintenance, referred to as "APTA" in the table. high platforms with high-floor vehicles and gain level access throughout. If low-floor vehicles are selected, basically, two choices exist--partial low-floor (PLF), which includes the type 4.12 Infrastructure Modification of vehicle being considered in this study, and 100-percent Circumstances can arise where the transit system modifies low-floor vehicles. track. Modifications might include removing redundant fea- The issue of adopting 100-percent low-floor cars was con- tures to allow easing of curves, eliminating problematic fea- sidered in TCRP Report 2 (Chapter 3). The study concluded tures, and so forth. Modifications should never "worsen" the that introduction into the United States and Canada on standards described in the preceding paragraphs. Modifica- entirely new systems might prove difficult because tion may require the addition of requirements that may appear "worse" (e.g., tighter radii because of introducing New systems might not wish to assume liability for speci- street running to a system previously confined to reserved fying lower buff loads, even though no technical reason was track). In all these cases, the modification must go through identified why this cannot be done. the following processes: 100-percent low-floor designs might not meet stringent U.S. and Canadian fire standards (ASTM E-119 was specif- Application of the fundamental guidance provided in ically cited). Guidelines 2 and 3 (see Section 4.3); Application of the proposed guidelines (see Section 4.9); The buff loads traditionally applied in the United States Acceptance; and are derived from the "2 g" formula (i.e., the vehicle should Revised maintenance guidelines with new manuals, train- sustain an end loading equivalent to twice its own mass). ing, and tolerances (see Section 4.11). This has not been the practice in Europe and, as a result, U.S. and Canadian LRVs tend to have heavier structures than their European counterparts. This is not always the case-- 4.13 Best Practice for New Jersey has used a 1-1.1 g formula. On the other hand, System Design some states (e.g., California) have regulated to the 2 g for- mula (2). TCRP Report 2 observed that U.S. systems tended 4.13.1 Basics to use higher speeds but many European systems are now This section considers the situation likely to arise in the operating at equivalent and higher speeds without the future where a totally new system is planned that is not con- higher buff loads. The buff load issue is a definite restriction strained by any existing design decisions or technology and for Type 3 systems, or Type 4 systems that include any Type will not need to link with an existing one. It will only be con- 3 track. However, an initiative is taking place to reconsider strained by federal, state, and other regulations. the FRA position about buff load requirements for joint use Basically, four types of transit system might use LFLRVs: tracks. Ten years on from the publication of TCRP Report 2, 1. Street running using embedded rail; greater availability and worldwide experience of 100-percent 2. Reserved track (e.g., using flat bottom rail, cross ties, and low-floor operation will begin to outweigh the liability issue. ballast or direct fixation); The researchers also suggest that the fire issue be considered 3. Transit sharing railroad tracks; and as a possible future TCRP research activity, taking into 4. Combinations of these. account, among other features, LFLRVs can operate on all these, and this will probably The environment of transit operations using 100-percent continue. There is no "right" solution for transit system types; low-floor cars, including the extent of tunnels;

OCR for page 47
48 The sources of fire under a low floor compared with a high Cars with all-conventional Jakobs bogies and lowered floor floor; and areas between. A European example with low-floor center Recent standards developed in Europe for fire safety on all sections is the Basel Be4/8. types of rail systems, including streetcar and light rail Low-floor trailer cars using small wheels and IRW trucks. systems. This appears to be an outdated concept. Examples exist in Rostock and Leipzig. Although the guidance that follows refers only to PLF cars, some of these types may also be affected by the issues Some vehicles have been built using EEF wheelsets but, fol- mentioned above that have stopped the introduction of 100- lowing the difficulties experienced with this type, no products percent low-floor cars. are available based on this concept. Given that the researchers did not consider these types of vehicle, no guidance specific to them is given in the notes that 4.13.2 Who Should Apply This Guidance? follow. It is assumed that systems will be using the center truck This section of guidance is important to all the organi- type. One area of future research could be to see if using these zations and individuals noted in Section 4.1. In particular other types would offer advantages in the U.S. and Canadian modifications to track should be of interest to their long- context. If the issues listed in Section 4.13.1 concerning the term strategies. Modifications to track will strongly introduction of 100-percent low-floor vehicles were addressed, influence this might influence future configurations and design of PLF types as well. Plans for future transit systems, Product development for the U.S. and Canadian market, 4.13.5 Infrastructure Guidelines and Changes in the regulatory framework. The track geometry standards listed under "new systems" in Section 4.9.2 would apply. New systems should consider using 115 RE rail. For embedded track, a matching grooved 4.13.3 Where Will It Apply? rail is RI59/13 or RI59N, although it is also possible to use By definition it can only apply to Situation E in Table 4-1 115 RE with a formed groove alongside. Specifications for (i.e., long-term new system applications with new designs of new lines should include features to make the track as rigid as vehicle). practical. The wheel-rail interface issues discussed in Section 4.9.4 will apply. The table column, Situation E (New vehicles), in Table 4-10 will apply. 4.13.4 Basic Vehicle Configuration The earlier guidance in this document has assumed the 4.13.6 Vehicle Specifications specific type of PLF LRV being studied in this research [i.e., Section 4.8 will apply, but will need to be reviewed for a one that has three sections, the center section mounted on a Type 3 (Joint transit/railroad) application and may only apply center truck with IRWs (see Section 4.4.3)]. However, other if Section 14.13.5 is fully applied. types are possible: A two-section vehicle with floating articulation and an 4.13.7 Other Guidelines independent wheel bogie under one of the body sections. The following sections will also apply in full to this situation: Because this arrangement has fewer degrees of freedom, it may offer better dynamic performance than the three- 4.5 Vehicle selection issues, section type under study. Examples are the Leipzig Leoliner 4.6. Vehicle maintenance guidelines, design and the LF2000 in Dessau. 4.7. Vehicle modification, As above but small-wheel solid axle trailer bogie under one 4.10. Operation of LFLRVs, of the sections. Examples are the Geneva and St. Etienne 4.11. Infrastructure maintenance standards, and Be4/6 designs. 4.12. Infrastructure modification. Cars with all-conventional bogies, floating articulations, and low-floor areas between bogies. Examples are the Although these are not system design issues as such, the sys- Sheffield GT8 and Zurich Forchbahn cars. tem design needs to consider that they should be in place.