A Revolution - serial trainline communications - Industry Overview

Railway Age, August, 1998 by Tom Sullivan

A Revolution in serial trainline Communications

Advanced communications protocols and converging serial trainline standards could pay big dividends in lower operating costs and more efficient train operation.

Tom Sullivan is a principal at Transportation Systems Design, which specializes in providing high-technology consulting to the rail transportation industry. He can be reached at tom.suiivan@tsd.org or (510) 531-8411.

As the rail industry enters the 21st Century, a quiet but dramatic revolution is taking place with new serial trainline communications. Benefits should be significant both to the early adopters as well as their end users. Railcar buyers and those designing new rail vehicles should be aware of what's happening in this field because those who miss the bus may be forced to endure expensive retrofits or simply go without the benefits this new technology will offer.

There is ample evidence to suggest these new standards will succeed not only because of the extensive effort going into developing them but also because of the support of key buyers who want it to happen.

MTA New York City Transit is the first U.S. transit property to fully embrace these key new serial communications protocols. In the rail freight world, the Conrail-CSX Transportation-Norfolk Southern Positive Train Control consortium recently specified a communications protocol that potentially defines PTC east of the Mississippi. In addition, the Association of American Railroads' Electronically Controlled Pneumatic Brake specifications have been carefully crafted to provide additional capacity so as to allow future health and status monitoring of key railcar subsystems.

Amazingly, all of these groups have independently specified the same standard communications protocol. But before going further, it's appropriate to review the history of trainline communications to better understand where these new standards fit in and why they are so important.

MANY FUNCTIONS, FEW WIRES

Until recently it was standard rail transit practice to dedicate one or more electric trainline wires to control or monitor each train function. For example, in a transit vehicle consist, one pair of trainlines might control all left side doors and another pair the right side. Door status also requires a pair of trainlines to report all left side doors closed and another pair is needed for the right side status. Clearly, using this traditional approach, the number of trainline wires grows quickly, which makes it impractical (even though highly desirable) to be able to report exactly which door failed. Doors are just one of many trainlined subsystems. More wires also mean more electric coupler pins, and that means higher failure rates.

Microprocessor-controlled systems are everywhere on rail transit vehicles today, but surprisingly these systems are generally unable to communicate with each other. In the absence of an advanced serial trainline communication protocol and uniform standards, an "electronic Tower of Babel" has developed that can be very difficult, if not impossible, for a car builder to sort out.

But wait, it gets worse.

NEW-TECHNOLOGY HEADACHES

San Francisco's new light rail vehicles are typical of new high technology cars that do not properly benefit from serial trainlines. Dan Rosen, a senior Muni transit manager, describes the operational effect of this problem: "When our train operators first board these vehicles they must enter their ID into Cubic electronic fare boxes. Then, similar information must be entered into the Motorola digital radios. After that, route data must be entered into Vetag transponder boxes to control surface track switches, and similar information must be entered for subway operation using the new Alcatel SELTRAC communications-based train control system. Following that, similar data is entered into Translite passenger information signs. Finally, a route code must be entered for the electronic route signs."

"Why," Rosen asks quite reasonably, "can t our operators simply swipe a card to enter all this information once?"

Good question, and in fact all the technology necessary to do this is available today. The historical problem is that coordinating vehicle sub-suppliers is like herding cats. Generally, suppliers all like to go in different directions, each developing its own proprietary, incompatible interface to lock buyers into using only their system. However, to understand how quickly this picture might change, one need only recall the rapid demise of proprietary fax machines and the explosive sale of new fax machines once "Group 3" became the new fax standard.

But why should these new serial trainline standards efforts succeed? Because of extensive participation by the rail transit industry and major participation from big buyers with a lot of industry savvy. Enter the IEEE Rail Transit Vehicle Interface Standards group and NYCT.

IEEE'S STANDARDIZATION EFFORTS

Funded by the federal Transit Cooperative Research Program, RTVIS Project G4 traces its roots to the early 1980s, when the Federal Transit Administration was initially interested in developing rail transit standards. Ron Kangas, director of FTA's Office of Technology, believes these new serial trainline standards are "both necessary and long overdue and that the overall benefits to suppliers, end users, and taxpayers will be paid for many times over."