Collision types: rear-end, T-bone, head-on, sideswipe

The CHP-555 convention

The CHP's traffic-collision report form marks vehicles as V1 and V2, draws the vehicles as rectangles in plan view, and records the direction of force with arrows and the point of impact with a dot. It is the convention every San Diego freeway collision report follows — and this file uses the same visual language, because it is the language the record speaks.

Rear-end

One vehicle strikes the rear of another in the same lane. The rear vehicle is presumed to control the spacing — Vehicle Code §21703 requires following at a distance that is reasonable and prudent — and the struck vehicle's occupants take the whiplash-class load. Vehicle damage is a poor predictor of injury here; the energy that accelerates the occupant is what injures.

T-bone

One vehicle's front meets another's side, usually at an intersection. The struck vehicle's door is the only structure between the impact and the occupant. Right-of-way rules decide the duties: §21800 (uncontrolled intersections), §21801 (left turns yield to oncoming traffic), and §21802 (stop signs).

Head-on

The two vehicles meet front-to-front; closing speed is the sum of both speeds — the highest-force geometry on the road. California requires driving on the right half of the roadway (§21650) and permits passing left only where the left side is clearly visible and free of oncoming traffic (§21751). A head-on collision commonly follows a center-line crossing.

Sideswipe

Lateral contact between vehicles traveling the same direction in adjacent lanes — often with a forced direction change after contact. The lane-change duties are on the moving vehicle: §22107 requires safety before moving from a lane, and §22108 requires a signal for the last 100 feet.