RAILROAD GLOSSARY Freight Rail Handbook AAR - Association of American Railroads The central coordinating and research agency of the North American rail industry. It deals with matters of common concern to member roads; operations, hardware standardization, regulatory matters research, safety, forecasts, finance, etc. It is dedicated to the standardization of processes and progress of the rail transportation industry. Actual Placement Physically placing a car for loading or unloading at a place designated by, or usually used by, the shipper or consignee. AEI See Automatic Equipment Identification. Alignment The position of track in the horizontal plane expressed as ‘tangent’ or ‘curve.’ Allowance A fixed sum granted as reimbursement, deduction, or repayment. Assigned Siding A side track owned by a transportation line and turned over to one or more industries or individuals for the loading and unloading of freight. “A” Unit (AKA “Lead Unit”) A locomotive unit equipped with a cab and operating controls. Automatic A term applied to devices which function through the exercise of inherent power, as distinguished from those in which the changes are made manually. Automatic Block Signal System (ABS) A series of consecutive blocks whose use is governed either by train actuated block signals or by certain conditions affecting the use of a block. Unless so specified, such signals do not authorize the movement of trains. Automatic Block System A series of consecutive blocks governed by block signals, cab signals, or both, actuated by a train or engine, or by certain conditions affecting the use of a block. Automatic Equipment Identification (AEI) An electronic scanning system that detects and records encoded information applied to the side of freight equipment. Such information includes the car initial and number, capacity, and other UMLER data. Back-Haul To transport a shipment back over part of a route which it has traveled. Bad Order Cars When a car inspector finds a defective car, he tacks a small card labeled “bad order” in bold lettering on or near the door of the car. That car may not be moved from the terminal where the inspection occurred until the necessary repairs are made. Ballast Selected material placed on the roadbed for the purpose of holding the track in line.