It is shown in the paper that long term developments in mobility and safety can be related by an evolutionary model of growth and risk adaptation. The model is applied to historical data of several countries (Japan, USA, UK, Germany) over long periods of time. Growth of mobility can be described by sigmoid curves with a saturation level (taken from biology or econometrics) and risk in road traffic as the fatality rate follows a decreasing adaptation curve (taken from mathematical learning theory). A single peaked curve for the road fatalities per year is a necessary result from saturating growth and steadily decreasing risk adaptation. Deviations from these monotonic macro-developments in mobility and risk are also time dependent and related. Deviations from sigmoid mobility growth tend to be cyclic and seem to be reflected in delayed and reduced cycles of deviations from the steadily decreasing fatality rate curves as a growth-dependent safety adaptation. On the basis of these time-related evolutionary trends and cycles, long term predictions are given. It is argued that the momentary stagnation in safety improvements in some countries are temporary cyclical effects of the recent larger increase in motorized mobility and stagnated decrease of the fatality rate. In the long run the increase of mobility levels off to a saturation level for motorization. As a consequence of the model and its fit to data, the fatality rate seems to decrease to virtually zero as time proceeds to infinity, but the injury rate seems to stabilize on a non-zero level. The impact of these new findings and of the underlying theory of evolution and adaptation are discussed, and the relation between mobility growth and risk adaptation are seen as a result of the technological evolution of traffic in a self-organizing socio-economic system. (Author/publisher).
Abstract