Secure the accident site if it is safe. Photographs should show lines of travel, visibility, slope width, markings, hazards and the positions of the people involved. Note the sequence with time, weather and the statements of everyone present.
Important records include accident reports, witness contacts, original messages and videos, and documents concerning an additional breach of duty. For an injury, file medical findings, invoices, sick leave records and the development of symptoms chronologically.
Recourse also requires payment records, settlements, admissions and communication between the parties. A clear damage schedule separates items already compensated from open claims and makes later allocation easier.