On the right track
How to evaluate communications systems technology to help drive safety and ensure reliability
By Wynton Habersham and Ali Siadati, Transit & Rail Group | HNTB
With transit agencies’ ongoing focus around state of good repair and ways to best modernize their systems, train control and communications systems provide one of the best pathways to ensuring safety, reliability and efficiency of rail systems.
While traditional methods for train control have continued to improve, communications-based train control (CBTC) represents one of the most promising advancements and one that could bring rapid progress to the public transportation industry.
With CBTC, agencies can leverage real-time communication between trains, equipment and control centers to fully optimize how rail systems operate and improve overall performance. This allows for dynamic separation of vehicles, real-time speed adjustments and more precise positioning of vehicles during operation. These efficiencies can allow agencies to increase throughput, while avoiding incidents through real-time data about train location.
But CBTC is not a plug and play solution.
An agency’s budget, age and size of its system, type of railcar fleet, ridership volumes and geography all must be considered when determining if CBTC is a good fit.
During the program and system inception phase, several major considerations and decisions will profoundly impact the implementation schedule, system complexity, lifecycle cost and overall success of the program.
Risk Assessment
Assessing risks, including security considerations is an important first step in the consideration of implementing CBTC. Because of its reliance on wireless communication between trains and operating systems, there are potential vulnerabilities that have the potential to compromise normal operations of a CBTC system.
It is important to address these risks and vulnerabilities early through the development of specific security plans and countermeasures. This should include regular security audits, along with data encryption and intrusion detection.
System Adaptability
Communications-based train control is built on the idea of redundancy. So as CBTC is implemented, it should be designed to be resilient, including fail-safe measures and necessary fallback systems to ensure a seamless operation. It is essential to determine the acceptable levels of service degradation and operational constraints that meet the needs of the operations in the event of a primary CBTC system failure. This will drive the design, complexity and the amount of auxiliary equipment associated with a fallback system. It also is important that CBTC systems integrate within existing infrastructure such as passenger information systems.
Equipment
CBTC requires investments in a wide range of equipment to ensure that the entire system operates seamlessly.
This begins with defining clear requirements for trains that are equipped with CBTC technology to address impacts of complexity to the overall system. Doing this will help maximize the effectiveness of CBTC, including precise positioning and movement control and real-time monitoring that reduces the risk of accidents and collisions.
Replacement of other assets related to the legacy signaling system will include switch machine and track-related components, as well as other legacy non-signaling system equipment.
Training and Knowledge Sharing
Workforce development and training also plays a critical role in the implementation of communications-based train control. Even before the system selection process, it can be valuable to train the workforce and operators on how CBTC systems function and the corresponding protocols and procedures to ensure that the signaling system functions safely and efficiently.
In some cases, organizations may convene a cross-functional group of workers to help manage the design and system development process for CBTC. A focus on collaborative knowledge sharing across the organization and ensuring that people are engaged early, will help to promote a CBTC system’s overall performance.
Testing
Once the decision has been made to move forward with implementing CBTC, testing and validation plays a crucial role in ensuring the system is safe and reliable. This could include various simulations, field trials and interoperability tests to confirm the system is functioning as intended.
Getting independent certification and validation before the system is implemented also is important. This will include safety verification and validation processes to assess a CBTC system in addition to analyzing different scenarios around avoidance of collisions, derailments, speeding and overall passenger safety. Engaging in and receiving certification independently will ensure a CBTC system is being implemented with the highest safety standards in mind.
Migration Strategy
To minimize risk, it is important for agencies to collaborate with CBTC suppliers on a detailed migration strategy. That could involve replacing the legacy signaling system entirely by equipping a sufficient number of trains with CBTC technology. If the network cannot be replaced in one go, trains should be double equipped to operate on both the fitted and unfitted parts of the network.
Another approach is to allow “mixed mode” operations by retaining the legacy system on the infrastructure and interfacing it with the new CBTC system to enable the progressive introduction of the fleet equipped with CBTC.
Planning for CBTC
CBTC can offer several significant benefits. However, implementing a CBTC system requires careful consideration of multiple factors, including safety, broad stakeholder engagement, as well as a commitment to training and robust security. In doing so, agencies have the opportunity to unleash the full potential of CBTC that will modernize the experiences of passenger rail travel.
Wynton Habersham
Ali Siadati