What does vehicle departure angle mean?

[McMadelyn]

Vehicle departure angle refers to the angle between the tangent line drawn from the rearmost protruding point of the vehicle to the rear wheels and the road surface when the vehicle is fully loaded and stationary. In other words, it is the maximum angle between the horizontal plane and the plane tangent to the outer edge of the rearmost wheel's tire. Any rigid component fixed to the vehicle behind the rearmost wheel must not extend below this plane. The departure angle is applicable when descending a slope. As the vehicle moves downhill, when the front wheels have already reached level ground while the rear wheels are still on the slope, whether the rear bumper will get stuck on the slope depends on the departure angle. A larger departure angle allows the vehicle to descend steeper slopes without worrying about the rear bumper getting stuck and immobilized.