AEI Railroad RF Identification Standards
The Association of American Railroads' AEI Standard S-9203 (was S-918 and T94) is no longer available to download from the site. You can order the latest AEI standard documents from the Association of American Railroads by going to https://aar.com/standards/publications.html. You want to purchase "Section K Part III Wayside Electronics and Mobile Worker Communications Architecture".
Tag Mounting
Two tags are mounted on each railcar, one on the left side, and one for the right.
It is extremely important that the tag designated as the Left tag be mounted on the left side of the railcar and the Right-designated tag on the right side. If they are not mounted on the correct sides, the wayside AEI reader will report the railcar’s orientation incorrectly.
The sides of a railcar are defined by their location relative to the handbrake end (called the B-end) of the railcar. Imagine standing on the track and looking directly at the handbrake. The left side of the car will be on your left, and the right side of the car will be on your right.
If the railcar has a hand brake on each end, the A and B end designations will be stenciled on the railcar, and the B end will be used as above to determine the left and right sides of the car.
Locomotives have F and R stenciled on each end to designate the front and rear of the locomotive. The rear end of the locomotive will be used as above to determine the left and right sides of the locomotive.