How To Know How Many Major Transport Accidents In Norway

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Eustacia Wilcox
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1 Major transport accidents in Norway: assessing long-term frequency and priorities for prevention Rune Elvik, Institute of Transport Economics, Oslo, Norway

2 Problems to be discussed How many major transport accidents can be expected to occur each year in Norway? What is the uncertainty of an estimate of the expected frequency of major transport accidents? Can formal techniques for decision analysis help in setting priorities for the prevention of major transport accidents? 2

What is the uncertainty of an estimate of the expected frequency of major

3 Major transport accidents Five or more fatalities Historical records for Norway Historical records for Great Britain Historical records for Europe Records may not be complete 3

records for Great Britain 1967-2001 Historical

4 Major transport accidents in Norway Number of major accidents and fatalities Aviation Railways Road transport Maritime Mode of transport Accidents Fatalities 4

150 100 50 0 423 360 85 56 21 25 13 4 Aviation Railways

5 Major transport accidents in Norway Accidents per year

6 Major transport accidents occur randomly Number of years with 0, 1, etc accidents Observed Poisson Number of accidents per year 6

4 3 2 1 0 5 8 8 7 5.7 4.5 3 2.7 1.1 1 0.

7 Road accident fatalities (all fatal accidents) in Norway Number of fatalities per year

Number of fatalities per year 400 300 200

8 Fatalities in rail transport (all fatal accidents) in Norway Number of fatalities per year

Number of fatalities per year 35 30 25 20 15

9 Aviation fatalities in Norway (all fatal accidents) Fatalities per year

10 Maritime fatalities in Norway Recreational boats included Fatalities per year

11 Some observations There is a trend for fatalities to decline in all modes of transport The occurrence of a major accident does not signal that safety has deteriorated The contribution of major accidents to total fatalities differs substantially between modes of transport 11

signal that safety has deteriorated The contribution of major

12 Observed and estimated long-term frequency of major transport accidents in Norway Number of accidents per year Observed frequency Estimated long-term frequency 0.00 Maritime Aviation Rail Road 12

70 0.60 0.50 0.40 0.30 0.20 0.10 0.70 0.66 0.50 0.13 0.10 0.59 0.

13 FN-curves for long-term frequency of major transport accidents in Norway F (accidents per year) Maritime Aviation Rail Road N (fatalities) 13

14 Probability of 0, 1 etc major accidents per year - low and high estimate Probability Low estimate High estimate Number of major accidents per year 14

25 0.20 0.15 Low estimate High estimate 0.10 0.05 0.

15 Conflicting policy objectives Maximum reduction of total fatalities Reducing differences in accident risk Reducing likelihood of major accidents These policy objectives cannot be reconciled by assigning monetary values to them 15

likelihood of major accidents These policy objectives

16 Implications of policy objectives Reducing total number of fatalities All fatalities prevented are valued the same Reducing differences in risk Preventing fatalities resulting from high risk is valued more highly than preventing fatalities resulting from low risk Reducing likelihood of major accidents Preventing several fatalities in one accident is valued more highly than preventing the same number of fatalities in single-fatality accidents 16

preventing fatalities resulting from low risk Reducing likelihood of major accidents Preventing several

17 Utility functions for policy objectives Value of fatalities prevented Reducing high risk Reducing total fatalities Preventing major accidents Number of fatalities prevented 17

18 A three dimensional representation Risk Number of fatal accidents Number of fatalities per accident 18

19 A multi attribute utility model 1. (Utility weight for objective 1) x (Outcome indicator for objective 1) + 2. (Utility weight for objective 2) x (Outcome indicator for objective 2) + 3. (Utility weight for objective 3) x (Outcome indicator for objective 3) = Total utility for all objectives 19

2. (Utility weight for objective 2) x (Outcome indicator for objective 2)

20 An illustration for road transport Utility weight = attributable risk All fatalities (objective 1) = High risk fatalities (objective 2 ) = Major accident fatalities (objective 3) = Outcome indicator = value of dimension All fatalities (objective 1) = 1.0 High risk fatalities (objective 2) = 5.5 Major accident fatalities (objective 3) =

340 Major accident fatalities (objective 3) = 0.

21 Total maximum utility (road) Overall attainable utility: (1 x 1) + (0.340 x 5.5) + (0.013 x 6.4) = 2.95 Contributions of objectives to overall utility: Reducing total fatalities 1.00/2.95 = 34% Reducing differences in risk 1.87/2.95 = 63% Reducing major accidents 0.08/2.95 = 3% 21

22 Discussion of the utility model The utility values are arbitrary The utility function involves double counting The utility model does not tell when benefits are greater than costs The utility model is very flexible and can incorporate all policy objectives 22

23 Conclusions The long term frequency of major transport accidents is very imperfectly known Major accidents occur at random, but are becoming less frequent The importance of preventing major accidents cannot be addressed by means of cost-benefit analysis 23