Roads need to cater safely for all users

Road design should reduce the probability of accidents in advance, by means of the infrastructural design, and where accidents do occur, the process which determines the severity of these accidents should be influenced such that the possibility of serious injury is virtually eliminated. Thus, a sustainable, safe traffic system has [72]:

The concept can be translated into some, more practically oriented, safety principles:

Standards and criteria for sight distance, horizontal and vertical alignment, and associated traffic control devices are based on the following driver performance characteristics: detection and recognition time, perception-reaction time, decision and response time, time to perform brake and accelerator movements, manoeuvre time, and (if applicable) time to shift gears. However, these values have typically been based on driving performance (or surrogate driving measures) of the entire driving population. The models underlying these design standards and criteria therefore have not, as a rule, included variations to account for the special characteristics or performance deficits consistently demonstrated in research on vulnerable road users. On that purpose, specific guidelines to address the needs of for these special user categories are often proposed [95].