The KarTrak system was developed by GTE Sylvania (Waltham, Massachusetts) in the 1960s to identify and track railroad cars and containers (e.g. SeaLand). It used a vertically-stacked series of color-coded reflective barcode labels from 3M to encode each car’s car number. The barcodes were read by mailbox-sized scanners installed trackside.
The KarTrak system gained wide-spread use in the late 1960s and 1970s, although by the late 1970s, it was largely abandoned. You can still spot the occassional KarTrak label on a railroad car. KarTrak is described in U.S. patents 3,225,177 and 3,275,477.
Online, more KarTrak information can be found within this PDF [no longer available online]. Some excerpts, which quote other publications:
The DM & IR [Duluth, Missabe and Iron Range Railroad installation is simple, yet effective. It depends on two unique system elements. A Sylvania KarTrak scanner and a permanent marking of Scotchlite reflective sheeting on the side of each car. The KarTrak scanner reads the special code marking of Scotchlite reflective sheeting. This pattern contains a start to read indication, room for variable information, and is followed by the empty or lightweight in long tons. The car number and the stop read mark. Both sides of the more than 9,000 cars and locomotives carry these markings. The KarTrak scanner turns on automatically as the train approaches. The scanner optically analyzes the identification markings, converts this information into electrical impulses, which are ultimately printed out on a tele-typewriter, paper or magnetic tape, or directly to a computer. This is made possible by feeding the electrical impulses from the scanner to the data processing equipment housed in this console. [Sylvania/3M promotional film]
By 1967 the [KarTrak] system was so successful that all North American railroads adopted the plan, followed soon after by the American Trucking Association, who put the codes on all trailers shipped by rail. At its high point, some seven years after its start, approximately 2,000,000 labeled cars, owned by 130 railroads, were spread over 135,000 miles of track. Most of the scanners were in place, the recording system was up and running, and the entire system was working the way it was planned. [Punch Cards To Bar Codes, 1997, p. 50, Benjamin Nelson]
By 1974, 95 percent of U.S. freight cars had been labeled. [The Bar Code Book, 1991, p. 13, Roger C. Palmer]
Update 3/17/2011: Just found this excellent article by David Jarrett Collins: Bar Codes: The 50th Anniversary of the First Bar Code Scanner.
Perhaps the earliest attempt at industry-wide use of bar codes was initiated in the late 1960s by the American Association of Railroads (AAR) to track railroad cars. It used a multi-colored bar code pattern and the first optical scanner to read the symbols.
This year, 2011, marks the 50th anniversary of the deployment of that first bar code scanner. It seems a suitable time to tell the story of how this development occurred.
Here’s a close-up of a well-worn KarTrak plate on Flickr.