First: check for injuries, get safe, and switch on hazards. For minor damage-only collisions, exchange details with the other driver and photograph everything — positions, damage, number plates and the road layout.
Where drivers agree on what happened, a completed front-to-rear statement of facts speeds everything up; where they don't, call the wardens and let them record it. Report to your insurer promptly either way. Being prepared turns a terrible day into an annoying one.
