How accurately does the public perceive differences in transport risks? TRB-paper Rune Elvik and Torkel Bjørnskau Published in Accident Analysis and Prevention 2005,

2 Survey of perceived risk of travel in Norway First made in 2000 Repeated in 2003 Sample size was 1,000 Basic question: –How safe do you think it is to travel by (car, bus, plane…)? –Very safe, safe, a little unsafe, very unsafe

3 Transport modes covered Car (role not specified) Car driver Motorcycle Bus Walking Cycling Commercial aviation Commercial ship (not recreational boats)

4 What do we know? Risk perception in the small and in the large The small is about specific hazards encountered when, e.g., driving The large is about societal risks, faced by everybody (not personal risks) Knowledge regarding relative risks is fairly accurate (modes are ranked correctly)

5 What do we know, continued The absolute number of accident victims is less accurately known Risks stated as fatality rates (5 x ) are poorly understood Differences in risks tend to be underestimated

6 An initial observation The distribution of answers between the categories (very safe, safe, a little unsafe, very unsafe) seemed to agree pretty well with actual differences in risk Actual differences = differences between modes in terms of fatality rate per billion kilometres of travel

7 Conversion of answers to scales representing perceived risk Can be done in many ways Four scales were developed: –A 100 (very unsafe) to 1 (very safe) scale –A 4 (very unsafe) to 1 (very safe) scale –A 10 (very unsafe) to 0.01 (very safe) scale –Odds of answering unsafe/safe The relationship between the mean values of these scales and fatality rate or injury rate was studied

8

9

10

11 Correlations between actual and perceived risk

12 Main conclusions The Norwegian public has an accurate perception of differences in risk between transport modes The range of values on scales developed to represent perceived numerically tends to be narrower than the range of actual differences in risk

13 Conclusions, continued The 10 to 0.01 scale correlates best with differences in statistically estimated risk Optimism bias is found: motorcycle riders think motorcycling is safer than the general public Recent major accidents appear to influence risk perception