12 TH INTERNATIONAL CONFERENCE: TRAFFIC SAFETY ON THREE CONTINENTS MOSCOW, 19-21 SEPTEMBER 2001 NIIAT, CSIR, FERSI, VTI, TRB, TRANSDEKRA, MTRF DEALING WITH LACK OF EXPOSURE DATA IN ROAD ACCIDENT ANALYSIS Dr. John Golias Associate Professor Dr. George Yannis Lecturer Department of Transportation Planning and Engineering National Technical University of Athens phone: +30.1.7721276, e-mail: igolias@central.ntua.gr Abstract Road accident analysis at national and international level is limited today by a number of problems inherent to the availability, the reliability, the comparability and the disaggregation level of exposure data. When adequate data are not available, then the use of alternative types of road accident analysis may produce reliable and useful results. This work identifies the basic insufficiencies inherent usually to the traffic data available at national and international level and the implications of this fact on accident analysis results. The use of absolute numbers and trends of values as well as of severity indices is generally free of the basic insufficiencies of exposure data but without useful information on accident rates. The use of induced exposure method and of accident type related percentages can provide useful information eliminating partially the need for exposure data. However, these methods which may answer a number of questions concerning road safety at international level should always be used with great care as interpretation of results may sometimes be a difficult exercise. Key-words: road safety, road accident, accident risk exposure, accident analysis, traffic data