Automatic Equipment Identification

Automatic Equipment Identification

Automatic Equipment Identification (AEI) is an electronic recognition system in use with the North American railroad industry. Consisting of passive tags mounted on each side of rolling stock, as well as active trackside readers, AEI utilizes RF technology to identify railroad equipment while en route.


In the late 1960s, railroads in North America began searching for a system that would allow them to automatically identify rail cars and other rolling stock. Through the efforts of the Association of American Railroads (AAR), an optical identification system was developed that used color-coded labels (similar to the bar code system). These labelswere mounted on each side of the rail car.

This early system was known as Automatic Car Identification (ACI, CarTrak). All rail car owners were required by the AAR to install ACI labels on their cars. This requirement lead to the full scale implementation of the ACI system in the early 1970s. Unfortunately, because dirt accumulated on the labels, and the labels began to deteriorate with age, the system's accuracy was much less than expected. ACI was eventually abandoned by the late 1970s. Because of this failure, the railroad industry did not seriously search for another system to identify rail cars until the mid-1980s.

Burlington Northern was the first railroad in North America to renew the search for an effective identification system. BN had been closely following the efforts of various maritime shipping companies, such as American President Lines, in their efforts to find a system to automatically identify containers. Based on the maritime companies' success with RF-based identification systems, Burlington Northern began a testing program in 1986.

Burlington Northern initially asked nine vendors to present their identification systems. From this group of nine, Burlington Northern selected two systems for full scale testing. The two vendors selected were General Railway Signal (GRS) and Union Switch & Signal (US&S). The Union Switch and Signal identification system is manufactured by Amtech Corporation of Dallas, Texas.

In January, 1988, Burlington Northern equipped 1,500 taconite (iron ore pellets) rail cars in northern Minnesota each with a GRS and an Amtech transponder. Each vendor also installed three wayside reader sites. All tags were mounted on the sides of the rail cars.

In August, 1988, the Burlington Northern Railroad presented a report on the results of their testing at the Association of American Railroads' Communication and Signal Annual Meeting. They stated that the accuracy of both systems over a six month period was in excess of 99.99%. Based on the spectacular results from both systems, the Burlington Northern asked the Association of American Railroads to form a committee to write an Automatic Equipment Identification (AEI) standard for the North American rail industry, and suggested that the AAR use the current draft ISO standard for container identification as a starting point.

A committee was formed by the Association of American Railroads, charged with the development of an Automatic Equipment Identification standard. Railroads, such as Norfolk Southern, Union Pacific, CSX, and Canadian National, began their own testing programs and reported the results to the AAR's AEI Committee.

In August, 1989, the AAR informed various identification system vendors that Amtech's identification technology had been selected as the Automatic Equipment Identification standard.

By the fall of 1989, the AAR's AEI Committee had selected a technology and defined the tag's data format. The only major decision that was still unresolved was the location of the tag on the rail car. This became a very controversial subject for the next nine months, as there were two groups of thought. One group wanted to place tags on the sides of the rail cars and another wanted them underneath. Each location had its advantages and disadvantages in terms of cost and maintainability. The tags were tested and found to operate well in both locations. It was finally decided by the AEI Committee in the summer of 1990 that two tags would be mounted on each rail car, one on each side.In July, 1990, the AAR Committee on Car Service sent a resolution to the O-T General Committee of the AAR to set a mandatory implementation date when all rail cars in interchange service would be tagged. The O-T General Committee is the highest operating committee within the AAR. The O-T General Committee requested that the AEI Committee perform a cost/benefit analysis on mandatory AEI implementation and recommend an implementation schedule. In October, 1990, the O-T General Committee approved the recommended AEI voluntary standard.

With these recommendations, in August, 1991, the O-T General Committee of the Association of American Railroads voted to make the AEI standard mandatory. The mandatory vote was ratified by the Association of American Railroads Board of Directors at their meeting in September, 1991. The mandatory period started on 1 March, 1992, and ended on 31 December, 1994. By the end of this period all 1.4 million rail cars in North American interchange service were to be tagged.

As part of the AAR's adoption of a standard based on Amtech technology, AAR required that Amtech license that technology. At the time of the AAR's 1991 mandate, six vendors sold AEI site equipment. Those vendors were Union Switch & Signal, Safetran, Harmon, VideoMasters, CCTC International in partnership with IBM, and Southern Technologies. [cite journal
last = Welty
first = Gus
title = Mandatory AEI tagging?
journal = Railway Age
month = March | year = 1991
url =
accessdate =
] As of August 2007, only two of these vendors remain, SAIC (formerly VideoMasters) and Southern Technologies.

As of 31 December, 1994, Amtech had shipped over 3.1 million tags to railways in North America. The AAR reported that over 95% of the North American rail car fleeted was tagged. Over 3,000 readers have been installed by the railways in North America as of the end of 2000.

Frequencies Used

The AAR's S-918 specifications outline ten recommended frequencies ranging from 902.250 to 921.500 MHz, depending on the location of the reading device (in a yard or trackside), with a nominal transmitting power of 2.0 Watts (measured at the transmitter).


External links

* -- A description of the earlier ACI barcode system

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