DEAD HEAD
A vehicle moving empty from one location to another.

DEAD LEVER
The truck brake lever (conventional system) that is directly connected to the truck bolster.

DEFECT CARD
A card issued by a railroad acknowledging responsibility for physical damage done to a non-owned railroad car and granting authority to bill the issuing carrier for the cost of repairs in accordance with the code of Interchange Rules published by the Association of American Railroads.

DEFECT CARD HOLDER
A metal or plastic receptacle positioned on the side of a car suitable for the containment and protection of defect cards.

DEMURRAGE
Charges assessed against a shipment which is detained beyond contracted time.

DENSITY
Weight per unit volume. For a commodity, usually expressed in lbs./cu. ft. or lbs./gal.

DENT
A deformation that changes the contour of a rail car from the original manufactured state.

DEPRECIATED VALUE (D/V)
The difference between the original cost of a tank car and the depreciation as calculated per AAR Rule 107. The resultant value is used in the settlement of damage claims.

DEPTH GAUGE
A device that allows for measuring the amount of liquid in a tank car.

DERAILMENT
Anytime the wheels of a car or an engine come off the head of rail.

DIP TUBE
See "Siphon Pipe."

DIRECT PAY MILEAGE
Mileage travelled which is reported and paid by the railroads to Union Tank Car, which in turn is passed directly to the applicable shippers. Contrast "Match."

DISMANTLER
A rail car to be sold for scrap.

DISPOSITION
Instructions stating where to ship a particular railcar. Generally, this includes not only the final destination, but also the specific RR lines on which the car is to be routed.

DOME
A stubby tank-like projection on top of a tank; now obsolete. This term is still sometimes used to refer to the top unload area.

DOT
The Department of Transportation. An agency of the U.S. government having jurisdiction over matters pertaining to all modes of transportation. The Federal Railroad Administration is the branch of the DOT that promulgates safety standards for rail equipment used in interchange.

DOT TANK CAR CLASS
Refers to tank cars built to the requirements contained in the code of Federal Regulations, Title 49, Sections 173.314, 173.319, 173.320 and Part 179 (inclusive). I. Non-Pressure Cars-111A: General purpose car with or without insulation. Tank can be carbon steel, stainless steel, or aluminum. 115A: Super insulated "Sandwich" type car. II. Pressure Cars-105A: Insulated car, no bottom outlet allowed. 112A: Non-insulated, car no bottom outlet allowed. 114A: Non-insulated car, bottom outlet optional. "A"-The letter "A" in the above classes indicates that the car is equipped with shelf couplers. "S"-If "A" is replaced with "S," then the car not only meets the "A" requirement, but, in addition is equipped with head shields. "J"-If "A" is replaced with "J," then the car meets both "A" & "S" requirements and, in addition, is equipped with thermal protection and meets special safety valve capacity requirements.

DOUBLE ROLLER STUCKI S.B.
A truck side bearing commonly applied to 100 ton cars. Marketed by A. Stucki Company. "See Side Bearing."

DOUBLE SHELF COUPLER
Couplers incorporating a feature designed to limit vertical movement between joined couplers thereby preventing accidental disengagement.

DRAFT GEAR
A cushioning or energy absorbing component mounted within the draft sill and yoke behind each coupler.

DRAFT GEAR CARRIER
The flat plate or plates attached to the underside of the draft sill to support the yoke and draft gear.

DRAFT GEAR POCKET
The space in a draft sill between the front and rear lugs in which the draft gear is mounted.

DRAFT KEY
See coupler cross key.

DRAFT LUG
One of a set of stops attached to the draft sill webs that transfer the forces received from the draft gear into the draft sill.

DRAFT SILL
The structure which connects the couplers to the tank and transmits the train loads.

DRAW BAR
An obsolete term sometimes used to refer to the car coupler.

DRY AIR PURGE
The process of blowing dry air into a tank for the purpose of reducing the moisture content of the tank atmosphere.

DTM
Refers to a direct-to-metal paint, one coat without a primer.