This paper describes the halo effects of a three-year automatic speed enforcement experiment on both driver behaviour and on accidents. The first year of this Finnish experiment comprised of the so-called before and after study on both experimental and on control roads. The two following years consisted of measuring the behavioural changes after the automatic surveillance system introduction. Only a crude description is given of the halo effects of speed. Important effects are: (1) The decrease in the share of speeding passenger cars on 80 km/h and on 100 km/h road sections has been greater in the test area than in the control area; and (2) the effect of the automated speed enforcement system on 100 km/h enforcement system on 100 km/h speed limit road sections seems to be somewhat greater than that on 80 km/h sections. In general, the number of accidents have been decreasing since the beginning of the experiment in the year 1990. Due to a rather short follow-up period, it is not possible to draw final conclusions related to the accident effects of the experiment. A three-year follow-up period will be undertaken in order to get a more reliable picture of the accident trend. This period will be closed in March 1995.
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