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From page 34... ... SECTION 9 34 CBTC Category Selection Process 9.1 Summary of Previous Sections The following table summarizes the differences among the project categories. Table 7: Summary of Functions by Category Category Type Possible back‐up for revenue service Support mixed‐ fleet to facilitate cut‐over Manage a single train with CBTC failure Manage work trains Drawbacks on deployment, maintenance, and CBTC operation availability 1.A Secondary System capable of revenue service 1.A.1 Secondary System capable of peak revenue service Yes Yes Yes Yes Major 1.A.2 Secondary System capable of off‐peak revenue service Yes, with performance degradation Yes, with phased implemen tation Yes Yes Major 1.B Secondary System designed to handle a single non‐CBTC train 1.B.1 Capable of one train per interstation Yes, with performance degradation No Yes Yes Moderate 1.B.2 Capable of one train in between two interlockings Not likely, but depends on the layout and off‐peak performance No Yes, but operating procedures needed Yes, but operating procedures needed Minor to moderate 1.B.2.1 With detection devices everywhere Not likely, but depends on the layout and off‐peak performance No Yes, but operating procedures needed. Procedures facilitated by knowledge of location of the train Yes, but operating procedures needed. Procedures facilitated by knowledge of location of the train Moderate 1.B.2.2 With detection devices only at interlocking Not likely, but depends on the layout and off‐peak performance No Yes, but operating procedures needed Yes, but operating procedures needed Minor Read the entire page →
From page 35... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 35 Category Type Possible back‐up for revenue service Support mixed‐ fleet to facilitate cut‐over Manage a single train with CBTC failure Manage work trains Drawbacks on deployment, maintenance, and CBTC operation availability 1.B.3 Without territory specific headway performance Not likely, but depends on the layout and off‐peak performance No Yes, but operating procedures needed. Procedures facilitated by knowledge of location of the train Yes, but operating procedures needed. Procedures facilitated by knowledge of location of the train Moderate 2 No secondary system No No Only by operating procedure Only by operating procedure None 9.2 Selection Criteria This section presents the various factors to be considered when evaluating the possible secondary systems appropriate for a specific transit agency. Selection of these factors was based primarily on the industry survey. These factors are driven by the following needs: 1. Mixed‐fleet operation during the cut‐over to CBTC 2. Read the entire page →
From page 36... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 36 • The new trains cannot use the legacy train control system to operate at a headway sufficient for revenue service. For instance, this is the case when the new trains cannot be equipped with the legacy system onboard equipment. Examples:  In a transformation to a CBTC driverless system, new trains are equipped with CBTC, while legacy trains, not equipped with CBTC, continue to provide revenue service. It is generally impractical to retrofit old trains with CBTC. In this case, the need for mixed‐fleet operation results in the selection of Category 1.A, an STD/PS capable of revenue service. Read the entire page →
From page 37... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 37 Starting with a Category 1.A.1 and going to a Category 1.B would require a large amount of effort and no such project could be found during the industry survey. This is technically feasible, provided that the legacy system is used as the secondary system temporarily. This option is discussed further in Section 9.3.2 Revisiting the Cut‐over Strategy. 9.2.2 Using the STD/PS as a Back‐up The reason for implementing STD/PS is often to use it as a back‐up system in case of CBTC failures, either wayside controller or train‐borne controller failure. Transit agencies may require a back‐up for the following reasons: First category of reasons is due to perception of the CBTC technology:  CBTC technology has not been commonly used in North America so far and though it is a proven technology with over 30 years of successful experience around the world, transit agencies in North America may still see it incorrectly as emerging.  CBTC relies heavily on electronic equipment, unlike some conventional signaling systems, and the technology gap between conventional signaling and CBTC may be too large for a transit agency to feel comfortable to depart from its legacy principles. Read the entire page →
From page 38... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 38 Further considerations An STD/PS capable of peak headway may be under consideration for brownfield projects, where the reason for deploying CBTC is only for continuous speed control. In this case, to simplify implementation of the CBTC system, the new CBTC is overlaid on top of the existing conventional signaling system. All other benefits of CBTC technology may be constrained by the underlying secondary system, especially the capacity increase, but the transition to CBTC is greatly simplified. Table 9: Meeting the Need to Operate a Peak Headway with the Secondary System Type Category Type Need for a peak headway Systems with STD/PS 1.A Secondary System capable of revenue service 1.A.1 Secondary System capable of peak revenue service  1.A.2 Secondary System capable of off‐peak revenue service 1.B Secondary System designed to handle a single non‐CBTC train 1.B.1 Capable of one train per interstation 1.B.2 Capable of one train in between two interlockings 1.B.3 Without territory specific headway performance Systems without STD/PS 2 No Secondary System 9.2.2.2 Operation at Off‐Peak Headway with STD/PS This need is based on whether an off‐peak revenue service is necessary in case of major CBTC system failure. From the industry survey, an STD/PS capable of off‐peak revenue service is deemed necessary for brownfield projects that have a high capacity demand with few or no alternative transportation modes and require other considerations such as crowd control on the platforms. Further considerations Though technically possible for greenfield projects, the industry survey did not identify any CBTC greenfield projects where a STD/PS capable of peak or off‐peak performance was selected. Read the entire page →
From page 39... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 39 Table 10: Meeting the Need for Back‐up for Revenue Service Type Category Type Need for back‐up for revenue service Systems with STD/PS 1.A Secondary System capable of revenue service 1.A.1 Secondary System capable of peak revenue service * (possible but unnecessary) Read the entire page →
From page 40... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 40 Table 11: Meeting the Need to Manage a Single Train with CBTC Failure with the Secondary System Type Category Type Manage a single train with CBTC failure Systems with STD/PS 1.A Secondary System capable of revenue service 1.A.1 Secondary System capable of peak revenue service  (possible but unnecessary) 1.A.2 Secondary System capable of off‐peak revenue service  (possible but unnecessary) Read the entire page →
From page 41... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 41 • There is no STD/PS (Category 2) . In this case, non‐equipped work trains are managed entirely by operating procedure. Read the entire page →
From page 42... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 42 9 – CBTC Category Selection Process, proposes a decision‐making method to evaluate the need for a secondary system, and Section 10 – Choosing the Secondary Method of Detection, presents a decision‐making method to evaluate the type of secondary train detection equipment. Broken rail detection has been widely perceived as an important feature in the application of track circuits, though it is not the primary function of a track circuit. However, its efficacy has been questioned, as noted in American Public Transportation Association (APTA) standard RT‐FS‐S‐002‐02, "Rail Transit Track Inspection and Maintenance," where it has been documented that "signal circuits do not provide 100 percent reliability for pull‐apart detection." Given that broken rails are a serious risk for train operation, agencies need to proactively detect rail flaws before the rail completely breaks. Broken rail detection with track circuits can only be effective when a track circuit is known to be vacant. That is, a broken rail is masked if there is a train occupying the track circuit. Under CBTC, especially during peak periods, trains are closely spaced and may be occupying most track circuits, rendering such broken rail detection ineffective. Effectiveness of broken rail detection is reduced even further with longer track circuits (such as might be found between stations or interlockings in Category 1.B) Read the entire page →
From page 43... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 43 9.3.1 Decision Flow Diagram In Figure 11, Decision Flow Diagram for STD/PS Selection, greenfield projects can skip the mixed‐fleet step and start with the need for peak revenue service provided by the STD/PS. The diamonds represent a functionality of the STD/PS. The diamonds are:  Mixed fleet during cut‐over: Is mixed fleet needed during the cut‐over to CBTC from the legacy train control system? See section 9.2.1 for information about making this decision. Read the entire page →
From page 44... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 44 Figure 11: Decision Flow Diagram for STD/PS Selection Mixed fleet during Cut‐over Peak performance Peak Performance permanently Off‐peak performance Manage single train with CBTC failure Manage unequipped work train 2 1.A.1 Yes During Cutover Yes Yes Yes No No No No No Yes 1.A.1 No : Need from STD/PS 1.A.2 Yes 1.B.1 1.B.2 1.B.3 (9.3.3) See 1.B Selection Flow Diagram (Figure 13) Read the entire page →
From page 45... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 45 9.3.2 Revisiting the Cut‐Over Strategy Most of the information presented in the previous sections is based on results from the industry survey. Regarding the cut‐over during the implementation of CBTC in brownfield projects, other possible cut‐ over methods can be considered. For projects where mixed‐fleet operation cannot be avoided, one possible method of cut‐over used in project Category 1.A is to start CBTC operations with a secondary system capable of peak revenue service. Then in a second step, remove some of the secondary signal equipment to reap the benefits of CBTC, eliminating the headway restrictions imposed by the STD/PS. Based on the industry survey this was done only for projects in Category 1.A, but not for other types of projects, such as Category 1.B and 2. Consideration should also be given to the transition process used when migrating to other categories of CBTC systems, such as 1.B or 2, where mixed‐fleet is only needed during the transition to CBTC, and not in the final configuration. The transit agency can consider deploying a system capable of mixed‐fleet operation (Category 1.A) followed by its decommissioning once the transition is complete, leading to Category 1.B or 2. Two possible options include: 1. Read the entire page →
From page 46... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 46 Figure 12 illustrates the adjusted Decision Flow Diagram: Figure 12: Alternate Decision Flow Diagram for STD/PS Selection Mixed fleet during cutover Peak performance Off‐peak performance 1.A.1 1.A.2 Yes During cutover Yes Yes No No 1.A.1 2 No Manage single train with CBTC failure Manage unequipped work train Yes Yes No No 1.B.1 1.B.2 1.B.3 (9.3.3) See 1.B Selection Flow Diagram (Figure 13) Read the entire page →
From page 47... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 47 9.3.3 Choosing Among 1.B Categories Table 13: Category 1.B Secondary Systems Designed to Handle a Single Non‐CBTC Train Category Type 1.B Secondary System designed to handle a single non‐CBTC train 1.B.1 Capable of one train per interstation 1.B.2 Capable of one train in between two interlockings 1.B.2.1 With detection devices everywhere 1.B.2.2 With detection devices only at interlocking 1.B.3 Without territory specific headway performance, with detection devices everywhere If the need for managing a single train with CBTC failure or non‐equipped work train is established, the level of STD/PS appropriate for a particular project must still be defined. Choosing among the 1.B Categories is the equivalent of fine‐tuning the level of STD/PS to implement. It is dependent on the track configuration and the capacity needed along the line which may not be the same between each pair of stations. The method for choosing between the 1.B Categories can be the following: 1. Choosing between Category 1.B.1, capable of one train per interstation, and Categories 1.B.2/1.B.3, not capable of one train per interstation 2. Read the entire page →
From page 48... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 48 9.3.3.2 Choosing Between Detection Devices Everywhere (Categories 1.B.2.1/1.B.3) and Only at Interlockings (Category 1.B.2.2) Read the entire page →
From page 49... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 49 In summary:  If the legacy system does not include a method of enforcement of signals, then options 1.B.2.1 or 1.B.3 can be used and are equivalent. There may be either signals without enforcement or switch position indicators.  If the legacy system includes a method of enforcement of signals and the method can be kept in the new system, option 1.B.2.1 is preferred. Read the entire page →
From page 50... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 50 9.4 Other Considerations 9.4.1 Other Potential Influences All the factors discussed previously are usually the main factors in the assessment done by engineering and operation departments. There are several other influences which may affect the decision process. Those influences may not be identified as factors, but may be in the decision maker's mind. For instance, if there is already significant solid‐state equipment in service or electronics onboard the trains, the agency may be more comfortable with CBTC technology, and may be less likely to require a high degree of back‐up by a secondary system. Below are some of the most common influences. 9.4.1.1 Supplier Influence • CBTC suppliers are adapting to client needs but are also capable of influencing transit agency selection regarding the STD/PS. • Though most of the CBTC suppliers are also track circuit vendors, most of them have been advocating for axle counters over track circuits. One reason is that axle counters can be installed independently of the existing signaling system, which works well for upgrade projects. Read the entire page →
From page 51... ... SECTION 9 – CBTC CATEGORY SELECTION PROCESS 51 rest of the network. The complexity of the rail network, and the intensity of the service to be provided on that network, is likely be a factor impacting the decision for a back‐up system. 9.4.2 Other Topics Not Usually Considered as Factors This section notes some of the possible issues which, after analysis of the industry survey, turned out to not be factors in the decision of which type of STD/PS to implement. 9.4.2.1 Underground/Above Ground Systems Based on the industry survey, there is no influence on the assessment whether the infrastructure is in tunnels, at grade, or above ground level. From the industry survey, respondents indicated that projects with above ground territory in harsh winter locations chose to implement track circuits because broken rails are more frequent in extreme weather conditions. On the other hand, projects have cited extreme weather conditions as a reason for not having a secondary method of detection, as devices on the roadbed fail too often and impact CBTC operation availability. 9.4.2.2 Type of Rolling Stock Whether the rolling stock is with steel wheels or with rubber tires, the industry survey did not show any relevant effect. Read the entire page →

From page 34...

... SECTION 9 34 CBTC Category Selection Process 9.1 Summary of Previous Sections The following table summarizes the differences among the project categories. Table 7: Summary of Functions by Category Category Type Possible back‐up for revenue service Support mixed‐ fleet to facilitate cut‐over Manage a single train with CBTC failure Manage work trains Drawbacks on deployment, maintenance, and CBTC operation availability 1.A Secondary System capable of revenue service 1.A.1 Secondary System capable of peak revenue service Yes Yes Yes Yes Major 1.A.2 Secondary System capable of off‐peak revenue service Yes, with performance degradation Yes, with phased implemen tation Yes Yes Major 1.B Secondary System designed to handle a single non‐CBTC train 1.B.1 Capable of one train per interstation Yes, with performance degradation No Yes Yes Moderate 1.B.2 Capable of one train in between two interlockings Not likely, but depends on the layout and off‐peak performance No Yes, but operating procedures needed Yes, but operating procedures needed Minor to moderate 1.B.2.1 With detection devices everywhere Not likely, but depends on the layout and off‐peak performance No Yes, but operating procedures needed. Procedures facilitated by knowledge of location of the train Yes, but operating procedures needed. Procedures facilitated by knowledge of location of the train Moderate 1.B.2.2 With detection devices only at interlocking Not likely, but depends on the layout and off‐peak performance No Yes, but operating procedures needed Yes, but operating procedures needed Minor