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From page 30... ...
SECTION 8 30 Work Trains Work trains are defined as maintenance vehicles used by the transit agencies to perform inspections or maintenance of the railroad infrastructure. The management of work trains is driven by different factors such as the age of the infrastructure, whether the revenue service is stopped overnight, and whether work trains need to run in between revenue service CBTC trains. Another factor is the current experience of the transit agency; a transit agency with a cab signaling system that has few signals or signals only at interlockings is already used to managing non‐equipped work trains. Equipping work trains is a difficult challenge because of the sheer number and variety of work trains. Fitting CBTC equipment on a train is a considerable investment. The different options, benefits, and consequences are presented in the following sections. In this document it should be understood that work trains are trains capable of being detected by the secondary detection system. Where maintenance equipment, such as hi‐rail vehicles, may not have steel wheel shunting sufficient for use by track circuits, or may not be able to be detected by wheel sensors for axle counters, following operating rules is the only alternative for CBTC projects. Equipping hi‐rail vehicles, for example, would be a tremendous customization effort generally not worth the investment. 8.1 Not Equipping Work Trains One option is to not equip the work trains at all. Management of the work trains depends on the type of secondary system, where Categories 1.A and 1.B.1 can manage work trains entirely on the signaling system without relying on operating procedures. Categories 1.B.2 and 1.B.3 can manage work trains using a mix of the signaling system and some operating procedures, while Category 2 relies completely on operating procedures. Table 6: Not Equipping Work Trains Type Category Sub‐category Not equipping work trains Systems with STD/PS 1.A Secondary System capable of revenue service 1.A.1 Secondary System capable of peak revenue service Fully supported by the signaling system 1.A.2 Secondary System capable of off‐peak revenue service Fully supported by the signaling system 1.B Secondary System designed to handle a single non‐CBTC train 1.B.1 Capable of one train per interstation Fully supported by the signaling system 1.B.2 Capable of one train in between two interlockings 1.B.2.1 With secondary detection method everywhere Relying partially on the signaling system and partially on operating procedures; Procedures are facilitated by the knowledge of the location of the train
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From page 31... ...
SECTION 8 – WORK TRAINS 31 Type Category Sub‐category Not equipping work trains 1.B.2.2 With secondary detection method only at interlocking Relying partially on the signaling system and partially on operating procedures 1.B.3 Without territory specific headway performance Relying on operating procedures facilitated by the knowledge of the location of the train Systems without STD/PS 2 No Secondary System Entirely relying on procedure The 1.B.2 Category is divided into 2 subcategories, 1.B.2.1 with detection devices everywhere, and 1.B.2.2 with detection devices only at interlockings. One of the reasons for having detection devices everywhere as in 1.B.2.1 and 1.B.3 is to be able to detect non‐equipped trains with finer resolution. By having detection of non‐equipped trains, CBTC can provide protection for those trains with smaller separation. 8.2 Equipping Work Trains It is technically possible to equip the work trains with CBTC. Each type of vehicle is fitted with an onboard controller adapted for the type of vehicle. Customization of the onboard equipment to fit and function properly on a work train requires a major design effort and may not be possible for the number of different types of work trains. The customization must be done for each type of work train. Major elements of this work include fitting the onboard controller in the work train, routing cables between controller and other components and sensors, developing interfaces with propulsion and braking systems, mounting transponder reader and speed sensors, designing and preparing drawings, testing, and post‐implementation modifications. To simplify integrating the onboard controller on the work train, it is possible that the onboard controller is implemented such that it has no control of the vehicle and thus no enforcement of speed or movement authority limit. In this case, the onboard controller only reports location of the trains to the wayside controller which provides protection from other CBTC trains and possibly some interlocking protection as well. Another possible mitigation is to equip only part of the work train fleet or only the locomotives that pull or push work cars. This avoids heavy investment of equipping all work trains but allows having CBTC protection for most of the work trains. Since only one extremity of the work consist may be equipped, neither the onboard equipment nor the wayside controller knows the length of the work train and assumptions must be made for front‐ and rear‐end protection. The industry survey showed that there appears to be no relation between equipping work trains and the category of CBTC project. Some CBTC projects with off‐peak performance (Category 1.A.2) have fully equipped some of their work trains, though those trains could be run without CBTC with minimal impact in revenue service. On the other hand, agencies with no STD/PS but with night closure, have decided to not equip the work trains at all. The influence of the night closure is more important than the capability of the secondary system.
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From page 32... ...
SECTION 8 – WORK TRAINS 32 8.3 Using a CBTC Equipped Trailer To avoid equipped maintenance vehicles, some transit agencies use a trailer equipped with CBTC which is then attached to the maintenance vehicle. The trailer reports location of one end of the consist to the wayside controller which provides protection from other CBTC trains and possibly some interlocking protection as well, such as locking switches based on the location of the trailer and its vehicle. This option is described in Case Study 1, AirTrain JFK. 8.4 Using a Separate Tracking System As discussed in previous options, locating the maintenance vehicles is a major concern for transit agencies. Considering that work trains usually operate at low speed, there may not be a need to have the complete CBTC ATP functions active, where the continuous speed control is not necessary for trains already running at low speed. However, protection of the work train from other CBTC revenue service is important and is possible only by knowing the work train location. Therefore, it is possible to use other creative methods of train localization integrated with the CBTC system to allow protection from other trains. These creative methods may be using Radio Frequency Identification (RFID) or a Global Navigation Satellite System (GNSS)
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From page 33... ...
SECTION 8 – WORK TRAINS 33 8.6 CBTC Work Zone Function CBTC systems include a function to enhance safety of roadway workers at work sites. This function can create a restriction on the mode of operations and/or speed of CBTC trains in a particular area of the track. The restriction can be, for instance, to inhibit automatic mode operation. Because not all trains might be CBTC trains, other protections in the field such as flags and lanterns are still used. This function provides protection for a specific zone which is captured at the control center on the ATS system. Though it is a powerful function, it does not solve the problem of transferring the work train from the storage area to the work site and then back to the storage area. Work Zones may be set based on train movement, blocking an entire area when the train is moving based on location reported by the crew on the work train, but it is not practical since it requires a lot of coordination between the crew and the control center. Similar to the Work Zone function, the CBTC system includes a function that limits only the speed of CBTC trains over a specified area. This is usually used in cases of degraded track conditions or on tracks adjacent to work zones.
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