Sir - In your October issue, you published an article on the Invensys TBS100 transmission-based train control system and the trade-offs between a distance-to-go implementation and a moving block design (RG 10.01 p689).
I found the article very informative, but it is important to stress that the problems which it associated with the concept of moving block are not applicable to all such systems. I suspect they are representative of the problems Invensys had trying to implement a moving block system on an operating railway.
By contrast, Alcatel has experienced considerable success with its driverless, moving block train control system. SelTrac MB has been in continuous revenue service for over 15 years, and is currently in operation with eight different transit authorities around the world.
As an example, the 29 km Vancouver Skytrain Line 1 supports scheduled operation at 88sec headways, and is capable of 45sec headway operation in large sections of track, to enable quick debunching with minimal impact on schedule recovery. Its current four-year rolling average availability, including delays due to bad weather, passenger incidents and a one-day strike, is 99·4%.
Mr Gillan implied that moving block had problems in meeting headway requirements due to capacity of the data link and communication delays, problems in achieving high availability, problems regulating trains, and problems handling infrastructure constraints such as emergency ventilation of tunnels.
All of these issues have been successfully addressed by SelTrac MB, and are managed intelligently by Alcatel’s System Management Centre, based on the SelNet Train Management & Control platform.
On another point, the article suggested that Invensys has had a great deal of difficulty getting transit and safety authorities to accept the removal of track circuits. This, again, is one of the advantages of a revenue-proven design.
SelTrac MB does vitally prove train completeness and address the safety issues associated with train length without the need for a complete secondary train detection system based on track circuits. It has a proven safety record of operation without track circuits with over 90 operating-years of service in Europe, North America, and Asia.
Firth Whitwam
SelTrac MB Product Manager
Alcatel Transport Automation Solutions
Toronto, Canada
