International comparisons of road safety using Singular Value Decomposition


Oppe, Siem



There is a general interest in the comparison of road safety developments in different countries. Comparisons have been made, based on absolute levels of accident or fatality risk or on the rate of change of functions regarding risk, the number of accidents, fatalities or injuries over time. Such comparisons are mostly based on single parameters. The method described here goes into more detail regarding similarities and dissimilarities of such developments, using a Singular Value Decomposition (SVD) technique. A first analysis was carried out on the number of fatalities in 24 countries (mainly European) over 28 years (1970 through 1997). The data was taken from the International Road Traffic and Accident Database (IRTAD), initiated by the Organisation for Economic Cooperation and Development (OECD). The year 1970 is the starting year; from this year onwards, annual data is available for a large number of countries. The analysis showed that most of the similarities and dissimilarities are represented by four dimensions. There turned out to be one major common trend describing the general decrease of the number of fatalities over time from the starting year 1970 onwards. It is well known that before 1970 the number of fatalities increased in many countries and decreased shortly afterwards. However, this trend cannot be shown because data from the period before 1970 is missing. For Greece, Korea, Spain and Portugal the trend is on average increasing instead of decreasing, in particular for Greece and Korea. In all other countries there is a decreasing trend, generally at the same level, except for New Zealand. Here the decrease is less marked than in most Western countries. On all four dimensions the similarities between the European countries were large, compared with non-European countries, except for Greece, Spain, Portugal, Hungary and the Czech Republic and to a minor extent for Ireland. Within the cluster of European countries sub-clusters may be distinguished. The developments in Germany and the Netherlands are for instance rather similar, and the same goes for Belgium, France, Switzerland and Austria. This suggests that, apart from economic developments, geographical and cultural factors are also important. The analysis is only applied to the total number of fatalities. The same procedure could be used to compare the fatality rates for countries for which traffic volume developments are known. Such analyses might help to understand the major factors that affect safety for countries in general.

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