What to include in an accident diagram: a practical checklist

The non-negotiables

Every accident diagram, no matter how simple, should contain:

• ▸The road layout, recognizable enough that someone who knows the location says "yes, that's the place".
• ▸Every involved vehicle, positioned and rotated as it was at impact, labeled V1, V2…
• ▸A direction-of-travel arrow for each vehicle.
• ▸The point of impact, marked explicitly with its own symbol.
• ▸Traffic controls that governed the movement: signs, lights, lane markings.
• ▸A north indicator and, if any distances are shown, a scale reference.

Identification turns a drawing into documentation

Add each vehicle's license plate and a short description — make, color, damage area. In My Traffic Sketch these print as a table under the diagram, so the reader never has to guess which rectangle is the Corolla.

If people outside vehicles were involved — pedestrians, cyclists — place and label them too (P1, P2…).

Measurements: a few good ones beat many rough ones

Include the distances that answer real questions: length of skid marks, distance from the crosswalk, final rest positions. Three verified measurements are worth more than ten guesses. Always treat diagram measurements as illustrative until independently verified.

What to leave out

Everything that did not influence the collision: buildings that played no role, every parked car on the block, decorative trees. A diagram is evidence of relevance — if an element did not matter, its presence suggests you thought it did.