The objective of this Diploma Thesis is to correlate traffic characteristics with road accident severity and probability. In order to achieve these objectives, data concerning the road accidents occurred on Kifisias Avenue in Athens, Greece, during the period 2006 – 2010 were collected from the database of the Department of Transportation Planning and Engineering of the NTUA. Subsequently, traffic data were obtained from the Traffic Management Centre of Athens. For the analysis, logistic regression mathematical models were developed. The application of these models indicates that road accident severity is correlated with the logarithm of traffic density, the type of vehicle and the type of accident. When data are separated in two groups of peak and off-peak hour accidents, the parameter of traffic density is the only one appearing to be statistically significant. Furthermore, traffic volume is the only parameter found with a statistically significant impact on accident probability.