•In this systematic review and meta-analysis, we extracted pooled odds ratio to assess the strength of relation between drowsy driving and traffic injury.•Based on the results, drowsy driving can increase the chance of road crashes occurrence by 1.29 to 1.34 times higher than driving without sleepiness. To assess whether drowsy driving can increase road traffic accident related deaths and injuries. Systematic review and meta-analysis. Cochrane Injuries Group Specialized Register, Cochrane Central Register of Controlled Trials, EMBASE, Medline, National Technical Information service, Psychlit, International Road Research Documentation, Transport Research Information Service, and web sites related to the road safety organization were searched; experts were contacted, conference proceedings were hand searched, and relevant reference lists were checked. We sought to identify all epidemiological studies, published in English language, which assessed the association between fatigued or sleepy driving and the occurrence of car crashes lead to death or injury. We conducted a systematic literature review with meta-analysis using PubMed, Google scholar and other valid databases to search for articles published from January 1980 through September 2016 to identify precise effect of drowsy driving on road traffic accidents. For each study odds ratio was calculated, the ratio of event odds in the drivers with drowsy driving divided by the drivers without drowsy driving, which were pooled to obtain an overall estimate using a fixed and random effects models. Fourteen articles satisfying inclusion criteria were identified that all of them were included in quantitative synthesis. Pooled odds ratio obtained by fixed and random effect models was 1.29 (95% CI 1.24 to 1.34) and 1.34 (95% CI 1.25 to 1.43), respectively. Our findings that obtained from meta-analysis (with high level of evidence) suggest a significant association between crash involvement and drowsy driving. It seems that establishment of strategies to reduce any risk factors of road traffic accident such as drowsy driving can be effective in decreasing traffic crashes.