Searching for electronic standards - American Association of Railroads revises standards for locomotive electronics

Railway Age, August, 2001 by Howard Moody, Dave Meeks

To promote a competitive supply market in railway electronics, AAR's Railway Electronics Task Force is making substantial revisions to Locomotive System Integration standards and specifications.

A significant portion of AAR mechanical rules and standards is devoted to freight cars and locomotives. The Manual of Standards and Recommended Practices (MSRP) was recently modified to incorporate locomotives as part of the North American Interchange Agreement, which has more than 1,000 signatories and subscribers.

New MSRP standards are currently under development to provide for interchange and a competitive supply market in railway electronics. The AAR Railway Electronics Task Force (RETF) manages the development of new standards and existing standards and specifications as engineering changes are proposed. The RETF is composed of railway officers, suppliers, and other interested parties. Its mission is to support the railroads in maintaining electronics standards and specifications. A configuration management plan establishes practices for all AAR-developed hardware, software, and documentation. The intent is to cover only AAR standards and specifications, and does not apply to those not maintained by AAR.

The RETF has published standards for EOT devices and AEI into a new Section K of the MSRP. In addition, a significant number of engineering changes for EOTs, ABI, and M-591--the operating display standards--have been evaluated and are being incorporated into the MSRP. The RETE is the focal point for this effort, but most of the standards are the responsibility of other AAR committees: Locomotive Committee, North American Joint Positive Train Control Management Committee, Wireless Communications Task Force, and Brake Systems Committee.

The configuration management process adopted by the RETF is structured to provide for expert analysis of all engineering changes to the standards in Section K as well as a review by stakeholder committees. A web page is being revised to provide for easy access to the proposed changes (called "system problem reports" or SPRs) and provide blank forms. In the interim, the points of contact listed below can provide those items.

Currently, the RETF is directing substantial revisions to Locomotive System Integration (LSI) standards and specifications. Though developed in the early 1990s, LSI did not achieve the level of interchangeability originally anticipated by some. Although the LSI standards were used extensively, more needs to be done to take advantage of changes in technology. The current LSI architecture does not make it easy to add functionality to an LSI-equipped locomotive, and additional functionality or changes to existing functionality are expensive and difficult to implement. In 2000, the AAR contracted with ARINC to revise LSI Communications Specification M-590, which formed the backbone of LSI standards. In the meantime, Architecture Specification M-591 has been modified to accommodate ECP brake implementation and reflect small changes recommended to the alarm and icon blocks. The illustration (opposite) shows the proposed M-591 layout.

The approach taken with the operating display is to identify screen areas for specific functions and then to characterize the functions, but not to require a specific appearance. That will allow suppliers and railroads to decide on the appearance and provide for migration to new technology. For instance, recent changes were made to the brake area to accommodate the display of information for electronically controlled pneumatic brakes, which requires a different set of information to be displayed than with current brake systems. With the approach taken on the standard, this can be done through changes to the functional characterizations and not to the display configuration, making it easier to implement to meet the requirements of the purchaser and still provide for ease of use in interchange service.

M-591 also is configured to provide for future growth with the required second display. Currently, the second display configuration is entirely optional for the user's own requirements. In case of a display screen failure, the requirement for two displays was to provide for important information on the second screen to be displayed in the center third of the remaining display with the required functions of the operating display taking up the remainder of the screen. This was also done in anticipation of adding safety-critical train control functions, for example, that might be displayed on the second screen, and would migrate to the operating display, in case of a single screen failure.

The revisions being contemplated for M-591 and M-590 are extensive. Aided by significant input from Electro-Motive Division of General Motors and GE Transportation Systems, the standards as proposed will considerably improve LSI. The original LSI was a "star" configured local area network (LAN). All message traffic between devices was routed through a central processor. In addition, all messages were application-specific. As a result, any modifications to any functional device or new components required software changes to the router and other affected boxes.