15
Chapter 2
Testing Communications-
Based Train Control
Kenneth Diemunsch
Contents
2.1 Introduction ............................................................................................... 16
2.2 Pros and Cons of Using CBTC System ......................................................18
2.2.1 Pros of CBTC .................................................................................18
2.2.2 Cons of CBTC ...............................................................................19
2.3 Dierent Types of CBTC Projects ..............................................................19
2.3.1 Installation on a New Line: Greeneld Project ...............................19
2.3.2 Migrating an Existing Line: Browneld Project ..............................20
2.4 CBTC Architecture .................................................................................... 21
2.5 Principles of CBTC Testing .......................................................................21
2.5.1 Reuse as Much as Possible from Previous Projects ...........................21
2.5.2 Test in Factory as Much as Possible ................................................22
2.5.3 Test All Safety-Related Items ..........................................................22
2.6 Environmental Tests...................................................................................23
2.6.1 EMC Tests ......................................................................................23
2.6.2 Climatic Conditions .......................................................................23
2.6.3 Mechanical Conditions ...................................................................24
2.6.4 Abrasive Conditions ........................................................................24
2.7 First Article Conguration Inspection .......................................................24
2.8 Factory Tests ..............................................................................................24
2.8.1 Factory Test Goals ..........................................................................25
2.8.2 Factory Setup ..................................................................................25
2.8.3 Dierent Types of Factory Tests .....................................................26
16 ◾ Advances in Communications-Based Train Control Systems
2.1 Introduction
Communications-based train control (CBTC) technology is the most advanced
train control system for urban railway infrastructures. It is very dierent from
conventional relay-based signaling systems and more complex than most cab sig-
naling systems. CBTC functions are numerous and highly complex with custom-
ized details for each project. ey cannot be tested for all possible conditions at
2.8.3.1 Product Factory Tests ............................................26
2.8.3.2 CBTC Supplier Internal Factory Testing ...............26
2.8.3.3 Factory Acceptance Test ........................................26
2.8.3.4 Description of the Tests to Be Performed ..............26
2.8.3.5 Major Challenges of Factory Tests .........................27
2.9 On-Board Integration Tests ......................................................................27
2.9.1 Rolling Stock Characterization Tests ........................................27
2.9.2 Mechanical and Electrical Tests ...............................................28
2.9.3 Static and Dynamic Post Installation Check Out Tests ............28
2.10 Test Track ................................................................................................28
2.10.1 Use of the Test Track ................................................................28
2.10.2 Test Track Equipment ..............................................................29
2.10.3 Location of the Test Track ........................................................29
2.11 On-Site Tests ............................................................................................30
2.11.1 Post Installation Check Out .....................................................30
2.11.2 DCS Tests ................................................................................30
2.11.2.1 Wayside Network Tests .........................................30
2.11.2.2 Radio Tests ............................................................ 31
2.11.3 Localization Tests .....................................................................32
2.11.4 Integration Tests .......................................................................32
2.11.4.1 Integration Tests: Internal to CBTC ......................32
2.11.4.2 Integration Tests: External to CBTC .....................33
2.11.5 Functional Tests ........................................................................33
2.11.6 ATO Tests .................................................................................35
2.11.7 ATS Tests ..................................................................................35
2.11.8 Site Acceptance Tests .................................................................35
2.11.9 Shadow Mode Tests ..................................................................36
2.11.10 Reliability, Availability, and Maintenance Tests........................36
2.11.10.1 Reliability and Availability Demonstration ............36
2.11.10.2 Maintainability Demonstration .............................37
2.12 CBTC Test Duration ...............................................................................38
2.13 Constraints on Field Tests ........................................................................38
2.14 Conclusion ...............................................................................................39
References .......................................................................................................... 40
Testing Communications-Based Train Control ◾ 17
all locations. Knowledge of the CBTC system and experience with train control
commissioning are key to performing enough tests to detect most issues but permit
the start of revenue service as early as possible. e testing strategy proposed by
the CBTC supplier is the result of years of experience with the goal of minimiz-
ing expensive eld tests while demonstrating that the system will work properly in
revenue service. Despite the numerous tests performed before revenue service, it is
inevitable that operating challenges will be faced during the rst months of CBTC
system operation.
CBTC suppliers have CBTC products corresponding to a specic system archi-
tecture with core functions that have been tested and operating in revenue service on
many transit properties. Most transit agencies require a service-proven technology
that they want to customize. e level of customization of the CBTC system for the
project is one of the main factors in the number of issues in the system. Inevitably,
on every CBTC project, customized functions are where most of the errors are
found. ey may be related to design or implementation. Some customizations are
inevitable, for instance, tment of the carborne equipment onto the train, or for
taking advantage of a new improved functionality of the product. CBTC suppli-
ers prefer to deploy a system as close as possible to their product which has been
intensively tested in previous projects. It is common that a transit agency insists
on buying an o-the-shelf CBTC system but ends up requiring many customized
functions. Understanding that the system is a proven technology customized for the
project is key to optimize the tests.
Testing of CBTC is done intensively in the factory. e factory setup allows
for testing of almost all functions and all situations. e functions that may not
be completely testable in the factory are related to the carborne controller (CC)
interfaces and to the eld characteristics such as train localization and radio cov-
erage. Apart from those items, in an ideal world, the tests in the eld would only
be for demonstration to the transit agency that the system meets the contract
requirements.
Today, most of the current CBTC projects are migration projects with the goal
to increase revenue service performance by replacing an existing signaling system
that has reached the end of life with the state-of-the-art CBTC technology. In
almost all upgrade projects, the transit agency requires that the transition to CBTC
system be performed with the least amount of impact on train service. is con-
straint increases the complexity of the project due to limited track access. In those
cases, CBTC testing must be optimized to the extreme in order to be able to deploy
the system while maintaining service.
e recent IEEE Std 1474.4-2011 Recommended Practice for Functional
Testing of a Communications-Based Train Control (CBTC) System [1] pro-
vides a good reference and describes how and where CBTC functions should
be tested. However, it does not describe the sequence of tests in the context of
a project where CBTC is deployed on a transit property. is chapter intends
to explain the reason for performing specic tests at the factory or in the eld
18 ◾ Advances in Communications-Based Train Control Systems
and to provide insight based on experience with several CBTC projects in the
last decade.
2.2 Pros and Cons of Using CBTC System
Before presenting the testing strategy, let us consider the reason why transit
agencies decide to use CBTC for new lines or for upgrading their signaling
system.
2.2.1 Pros of CBTC
e main reasons for a transit agency to select CBTC technology are:
◾ Safety. CBTC includes continuous automatic train protection (ATP). Many
conventional signaling systems enforce the speed of the train only at certain
locations using grade time signals. After the train engineer accepts such sig-
nal, the train may then be operated to its maximum speed until the next red
signal. is results in intermittent speed control that relies on human inter-
vention not supervised by any system.
◾ roughput. CBTC uses a moving or xed virtual block system that allows
trains to follow each other very closely resulting in improved headway per-
formance. For projects with track circuits, more than one CBTC-equipped
train can occupy an individual track circuit at any time, whereas conventional
signaling system requires one or several track circuits between trains. In busy
transit systems, a goal of CBTC migration is to improve minimum headway
between trains.
◾ Automatic train operation (ATO). e CBTC system includes an ATO mode
that enables the CC to control the movement of the train without the train
engineer controlling the rolling stock master controller. e ATO mode pro-
vides a smoother ride for passengers, results in more predictable operation,
and enables energy saving. ATO operation can be associated with driverless
operation for additional benets. ATO is also possible with other types of
train control implementations.
◾ Positive train control (PTC) compliant. CBTC is a type of PTC, including
work zone and slow speed order enforcement that comply with the Railway
Safety Improvement Act of 2008 mandated by the U.S. Congress. erefore,
CBTC is a potential PTC solution for U.S. railroads under the jurisdiction of
the Federal Railroad Administration.
◾ High system availability. CBTC includes redundancy and built-in diagnostic
systems which report the status of most equipment to the automatic train
supervision (ATS). ese functions are also possible with other types of train
control implementations.
Testing Communications-Based Train Control ◾ 19
◾ Reduced maintenance cost. CBTC has less equipment than conventional
signaling systems, in particular on the trackside.
◾ CBTC has been deployed for more 30 years all over the world and is now a
proven technology.
2.2.2 Cons of CBTC
CBTC technology also comes with several challenges for transit agencies:
◾ Initial investment cost of deploying the technology may be higher than other
types of train control. Design, hardware, installation, and testing of CBTC
require years of eort and usually take longer than expected.
◾ e system is not modiable by the transit agency for dierent reasons. e
rst reason is technical: the computer skills required may not be available
within the agency. e second reason is the responsibility: the original equip-
ment manufacturer (OEM) is liable to provide a safe system to the transit
agency. Transit agencies do not want to accept the responsibility for changing
such complex system. Any change has to be carried out by the OEM. Note
that there are eorts by large transit agencies such as New York City Transit
and Régie Autonome des Transports Parisiens to specify interoperability and
compatibility of products across multiple CBTC vendors.
◾ CBTC technology is very dierent from traditional relay-based signaling sys-
tem, and, therefore, the transit agency must adapt to it. It requires new skills
for engineering and maintenance personnel as well as a new organization in
the transit agency.
2.3 Different Types of CBTC Projects
2.3.1 Installation on a New Line: Greeneld Project
e term “greeneld project” refers to the case where a transit agency is building
a new line. e railway project involves all aspects of railway engineering such
as civil engineering, track installation, traction power system, Rolling Stock and
the signaling system. In the early 1980s, CBTC started to be implemented on
such projects. Only after the technology was considered matured and experi-
ence was sucient, CBTC was applied to lines already in service as described in
Section 2.3.2.
ough new line schedules are more and more challenging, testing the signal-
ing system on a greeneld project is facilitated with easier track access than on a
project where the line is used for passenger service. Flexibility of track access is not
the only advantage of testing on greeneld projects, but it is by far the most impor-
tant. Access can be more frequent and reorganized at the last minute depending on
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