Road traffic safety refers to the methods and measures, such as traffic calming, to prevent road users from being killed or seriously injured. Typical road users include pedestrians, cyclists, motorists, passengers of vehicles, and passengers of on-road public transport, mainly buses and trams.

Best practices in modern road safety strategy:

The basic strategy of a Safe System approach is to ensure that in the event of a crash, the impact energies remain below the threshold likely to produce either death or serious injury. This threshold will vary from crash scenario to crash scenario, depending upon the level of protection offered to the road users involved. For example, the chances of survival for an unprotected pedestrian hit by a vehicle diminish rapidly at speeds greater than 30 km/h, whereas for a properly restrained motor vehicle occupant the critical impact speed is 50 km/h (for side impact crashes) and 70 km/h (for head-on crashes).

— International Transport Forum, Towards Zero, Ambitious Road Safety Targets and the Safe System Approach, Executive Summary page 19

As sustainable solutions for classes of road safety have not been identified, particularly low-traffic rural and remote roads, a hierarchy of control should be applied, similar to classifications used to improve occupational safety and health. At the highest level is sustainable prevention of serious injury and death crashes, with sustainable requiring all key result areas to be considered. At the second level is real-time risk reduction, which involves providing users at severe risk with a specific warning to enable them to take mitigating action. The third level is about reducing the crash risk which involves applying the road-design standards and guidelines (such as from AASHTO), improving driver behavior and enforcement. It is important to note that drivers' traffic behaviors are significantly influenced by their perceptions and attitudes.

Traffic safety has been studied as a science for more than 75 years.

Traffic collisions have become one of the world's largest public-health and injury-prevention problems. The issue is all the more acute because the victims are overwhelmingly healthy before their crashes. According to the World Health Organization (WHO), more than 1 million people are killed on the world's roads each year. A report published by the WHO in 2004 estimated that some 1.2 million people were killed and 50 million injured in traffic collisions on the roads around the world each year and that traffic accidents were the leading cause of death among children 10–19 years of age. The report also noted that the problem was most severe in developing countries and that simple prevention-measures could halve the number of deaths.

The standard measures used in assessing road safety interventions are fatalities and killed-or-seriously-injured (KSI) rates, usually expressed per billion (10⁹) passenger kilometres. Countries using older road-safety paradigms replace KSI rates with crash rates – for example, crashes per million vehicle-miles.