In this study, the connection between driving speed and the safety of pedestrians has been estimated by applying a new mathematical method based on the random nature of accidents and the theory of probability. The relationship between the degree of seriousness of an accident and the collision speed is defined on the basis of the results of previously documented case studies. The interdependence between vehicular speed, the probability of accidents, and collision speed is examined by theoretical computations. Initially, a traffic flow at a constant speed into which a pedestrian appears wholly at random is considered. Thereafter, the possible interdependence between the pedestrian's behavior and the approaching vehicles, the pedestrian's movement across the street as well as the distributions of speeds and headways is dealt with. The risk of death is chosen as the measure of pedestrian safety. It indicates the probability of a pedestrian being run-over by a vehicle and, having been run-over, the probability of death. The explanatory variables are vehicle speed, driver's breaking reaction time, deceleration of the vehicle and the time that the pedestrian remains in the vehicle's collision course. The influence of the pedestrian's behavior has been studied with four models of susceptibility: the wholly random model (A) and the model dependent on vehicular speed (B), on time-interval (C) and on noise levels (D). Model A was chosen. According to the model, pedestrian safety depends to an alarming degree on vehicular speed. An excess speed of 15 km/hour is 2.5 times more dangerous than driving at the legal permitted limit of 50 km/hour in built-up areas. Furthermore, 50 km/h speed causes a risk of death almost eight times higher when compared with a speed of 30 km/h. Vehicular speed has such a dramatic effect on the safety of pedestrians that society must get more effective tools to regulate speeds, at least in streets where pedestrians predominate. For this reason it is recommended that current police enforcement activities be supplemented by a communal speed control system.

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    Helsinki University, Finland

    Hallituskatu 8
    00100 Helsinki,   Finland 
  • Authors:
    • PASANEN, E
  • Publication Date: 1990-11


  • Finnish

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  • Accession Number: 00622031
  • Record Type: Publication
  • ISBN: 951-22-0487-8
  • Files: TRIS
  • Created Date: May 31 1992 12:00AM