This Diploma Thesis aims to investigate the influence of summer time change on Road Safety. It is important to investigate the impact of this particular measure, as it causes changes on the lighting conditions which is one of the accident causes. Following bibliography research referring to similar works, appropriate data on road accidents, traffic volumes and solar circle calendar were collected and subsequently processed. The results of this processing pointed out that impact of summer time change to Road Safety is not negligible. Spring summer time change leads to an increase of 3% of the relative accident index, whereas the autumn summer time change leads to the corresponding decrease of this index. The similar results were also found at the macroscopic comparisons of monthly distribution of accident and traffic volume data.