Departure angle
Also called rear departure angle
Departure angle is the steepest slope a vehicle can back down or drive off without dragging its tail, measured between the ground and a line from the rear tire's contact patch to the lowest point behind it.
What is departure angle?
The same geometry as approach angle, taken at the other end. Draw a line back and up from where the rear tire touches the ground until it meets the lowest thing hanging off the back. That angle is what you have when you crest a ledge and the back of the truck has to follow the front over it.
It gets less attention than approach angle and it is usually worse, because the back of a vehicle is where the accessories accumulate. The definitions run in parallel with approach angle: US federal law words it identically but tangent to the rear tire and touching the underside rearward of it, SAE J1100 covers both under dimension A106, and ISO 612:1978 puts it at paragraph 6.11. Both the European and the American rulebooks want at least 20 degrees of it before they will call a light vehicle an off-roader.
What eats it
A tow hitch receiver, almost always. It hangs below the bumper by design and it is the first thing to touch on most trucks. A hitch-mounted bike rack or cargo tray is worse again, and a trailer is a different problem entirely. After that: the rear bumper's lower edge, a spare tire carrier, exhaust tips, and on a long-bed truck the overhang itself.
Rear overhang is the structural version of the problem. The further the body extends behind the rear axle, the worse the angle, and that is fixed at the factory. A short-bed truck has a real advantage here that no modification gives back to a long bed.
See also
Seen in
Sources
- 49 CFR 523.2 and 523.5, Definitions and Light truck, Electronic Code of Federal Regulations, read 2026-08-27The fuel economy rules, of all places, are where United States federal law writes down what approach, departure and breakover angle mean. Free and quotable, unlike every dedicated standard on the subject.
- Regulation (EU) 2018/858, Annex I Part A and Appendix 1, Procedure for checking whether a vehicle can be categorised as off-road vehicle, Official Journal of the European Union, L 151, 14 June 2018, CELEX 32018R0858, read 2026-08-27The rare case of a legal definition of an off-road vehicle with numbers in it. It defines ground clearance itself and cross-refers the three angles to ISO 612:1978 paragraphs 6.9, 6.10 and 6.11. ISO 612 is paywalled (https://committee.iso.org/standard/4729.html); this regulation is free and names the paragraphs. The American equivalent is SAE J1100, Motor Vehicle Dimensions, also paywalled (https://saemobilus.sae.org/standards/j1100_200911-motor-vehicle-dimensions) and cited by name in 49 CFR 571.3.