The mortality and morbidity of road traffic accidents (RTA) is increasing in the South Asian region, including Sri Lanka. Therefore, the demographic factors, types of vehicles involved, and the severity of injuries sustained in RTA was studied. Age, gender, and details of the incident of all patients admitted to hospital following a RTA, between January 2007 and August 2012, were obtained by interview. Following a medico-legal examination, the type and severity of injuries was categorized as, non-grievous, grievous, endangering life or fatal in the ordinary course of nature. Of the 579 RTA casualties examined, 72% were males, 28% females, and 26% were in the 20–29 year age group. There were 44% passengers, 32% drivers, and 20% pedestrians. Of the 440 vehicle occupants, 37% were on motor cycles, 28% in three wheelers, 13% in dual purpose vehicles and 11% in buses. Of the 114 pedestrians, 33% had been struck by motor cycles, 19% by three-wheelers and 17% by dual purpose vehicles. There was at least one soft tissue injury in 84%, whilst 45% had one or more fractures. In 85% of bicycle riders, the injuries were grievous, endangering life or fatal in the ordinary course of nature. A high proportion of young adults sustained grievous injuries due to RTA. Almost two thirds of the casualties resulted from motorcycle or three wheeler accidents. Laws limiting the number of passengers carried, installation of side doors, mandatory use of seat belts in three wheelers, and protective garments for motorcyclists are recommended.