The present Diploma Thesis aims to investigate the effect of vehicle collision type on road accident severity in Greece. For the achievement of this objective, appropriately processed data for the period 2007-2011 in Greece were used from the database of the Department of Transportation Planning and Engineering of the National Technical University of Athens (NTUA) and the log-rate analysis models were developed. Severity has been chosen to be expressed as the rate of number of persons killed and seriously injured divided by the number of slightly injured persons. The analysis led to the investigation of the impact of the chosen parameters, which are region type, vehicle type involved, on accident severity. It appears that the severity is higher for the passengers of passenger cars and motorcycles, while the vehicle type of the opponent car that affects more the severity is passenger car and truck. This impact is higher outside urban areas.