【正文】 f accidents may be regarded as one plicated accident with many cars assumption does not apply to are often related to the same accident and therefore the independency assumption does not second assumption seems less obvious at first occurrence of accidents through time or on different locations are not equally , the assumption need not hold over long time is a rather theoretical assumption in its it holds for short periods of time, then it also holds for long periods, because the sum of Poisson distributed variables, even if their Poisson rates are different, is also Poisson Poisson rate for the sum of these periods is then equal to the sum of the Poisson rates for these assumption that really counts for a parison of(posite)situations, is whether two outes from an aggregation of situations in time and/or space, have a parable mix of basic ., the parison of the number of accidents on one particular day of the year, as pared to another day(the next day, or the same day of the next week etc.).If the conditions are assumed to be the same(same duration, same mix of traffic and situations, same weather conditions etc.)then the resulting numbers of accidents are the outes of the same Poisson assumption can be tested by estimating the rate parameter on the basis of the two observed values(the estimate being the average of the two values).Probability theory can be used to pute the likelihood of the equality assumption, given the two observations and their statistical procedure is rather Poisson assumption is investigated many times and turns out to be supported by a vast body of empirical has been applied in numerous situations to find out whether differences in observed numbers of accidents suggest real differences in main purpose of this procedure is to detect differences in may be a difference over time, or between different places or between different differences may guide the process of the main concern is to reduce the 7number of accidents, such an analysis may lead to the most promising areas for necessary condition for the application of such a test is, that the numbers of accidents to be pared are large enough to show existing many local cases an application is not blackspot analysis is often hindered by this limitation, ., if such a test is applied to find out whether the number of accidents at a particular location is higher than procedure described can also be used if the accidents are classified according to a number of characteristics to find promising safety only with aggregation, but also with disaggregation the Poisson assumption holds, and the accident numbers can be tested against each other on the basis of the Poisson a test is rather cumbersome, because for each particular case, each different Poisson parameter, the probabilities for all possible outes must be puted to apply the practice, this is not necessary when the numbers are the Poisson distribution can be approximated by a Normal distribution, with mean and variance equal to the Poisson the mean value and the variance of a Normal distribution are given, all tests can be rephrased in terms of the standard Normal distribution with zero mean and variance putations are necessary any more, but test statistics can be drawn from use of accident statistics for traffic safety testing procedure described has its merits for those types of analysis that are based on the assumptions best example of such an application is the monitoring of safety for a country or region over a year, using the total number of accidents(eventually of a particular type, such as fatal accidents), in order to pare this number with the oute of the year sequences of accidents are given over several years, then trends in the developments can be detected and accident numbers predicted for following such a trend is established, then the value for the next year or years can be predicted, together with its error from a given trend can also be tested afterwards, and new actions most famous one is carried out by Smeed will discuss this type of accident analysis in more detail application of the Chisquare test for interaction is generalised to higher order and Lane(1974), in measuring the effect of pulsory wearing of seat belts, were among the first who applied the partitioning of the total Chisquare in values for the higher order interactions of fourway are not restricted to overall effects, but Chisquare values can be deposed regarding subhypotheses within the in the twoway table, the total Chisquare can be deposed into interaction effects of part advantage of previous situations is, that large numbers of Chisquare tests on many interrelated(sub)tables andcorresponding Chisquares were replaced by one analysis with an exact portioning of one attention is put to parameter ., the partitioning of the Chisquare made it possible to test for linear or quadratic restraints on the rowparameters or for discontinuities in unit of analysis is generalised from counts to weighted is especially advantageous for road safety analyses, where corrections for period of time, number of road users, number of locations or number of vehicle kilometres is often last option is not found in many statistical 1977 gives an example for road safety analysis in a twoway puter programme WPM, developed for this type of analysis of multiway tables, is available at SWOV(see: De Leeuw and Oppe 1976).The accident analysis at this level is not tries to detect safety problems that need special basic information needed consists of accident numbers, to describe the total amount of unsafety, and exposure data to calculate risks and to find situations or(groups of)road users with a high level of analysis for research safety research is concerned with the occurrence of accidents and their , one might say that the object of research is the researchers interest however is less focused at this final oute itself, but much more at the process