Wired vs. wireless E-P brakes: the debate continues

Railway Age, Jan, 1997

The debate continues--wired vs. wireless for electro-pneumatic brake system control-and TSM, Inc., has checked in to address what it calls "several misconceptions" regarding the issues. TSM makes its points strongly on the side of wire-line control, with these observations:

5: With wired technology, all cars operate independently, so a car (or cars) can experience a failure without affecting the entire train. In the event of a failure, a fault message is sent to the locomotive and "the train continues to operate normally." Diagnostics would also alert the engineer in the event of a trainline cable separation, something that TSM says hasn't happened in more than 55 million car-miles of service with its system.

* With either type of communications system, all cars must be equipped with e-p brakes, otherwise the train should operate using only its conventional pneumatic braking system. Why? With radio-equipped cars repeating what the brake pipe indicates, TSM says, some portions of the train will apply and release brakes more quickly than with pure pneumatic operation, and "the train-handling effects caused by this action are undesirable."

* If cars have been inactive long enough to discharge their batteries, all cars can be simultaneously charged through the cable, but with a radio system, batteries must be replaced or individually charged before the cars' brake systems can become operational.

* With a hard-wired system, there are no problems with so-called "shadow zones" where radio signals cannot be received, or with interference or differentiating among signals in congested areas.

Obviously, TSM's interest is in promoting the system it has in revenue and test service now, as the Association of American Railroads works toward completion of e-p brake system specifications. Just as obviously, those backing an RF-based system will also be heard from.