Mandating seat belt use has been shown in many jurisdictions to be the most effective immediate way of significantly reducing death and severe injuries resulting from motor vehicle collisions. Historically tort law has played an important role in deterring certain types of conduct. It appears that if the common law continues to develop by itself, the seat belt defence will be increasingly recognized by the courts in assessment of contributory negligence. If seat belt defence is to be recognized by law, such statutes should be broad rather than restrictive to provide just penalty for unreasonable behaviour on the part of an individual by which he contributes to injuries caused him by someone else's negligent acts.