OBJECTIVE: To investigate the clinical characteristics of patients involved in road traffic accidents according to the New Injury Severity Score (NISS). METHODS: In this study, medical records of 1,048 patients admitted at three hospitals located in different regions between January and December 2014 were retrospectively reviewed. Only patients who received inpatient treatments covered by automobile insurance during the period were included. Accidents were classified as pedestrian, driver, passenger, motorcycle, or bicycle; and the severity of injury was assessed by the NISS. RESULTS: The proportion of pedestrian traffic accident (TA) was the highest, followed by driver, passenger, motorcycle and bicycle TA. The mean NISS was significantly higher in pedestrian and motorcycle TAs and lower in passenger TA. Analysis of differences in mean hospital length of stay (HLS) according to NISS injury severity revealed 4.97±4.86 days in the minor injury group, 8.91±5.93 days in the moderate injury group, 15.46±11.16 days in the serious injury group, 24.73±17.03 days in the severe injury group, and 30.86±34.03 days in the critical injury group (p<0.05). CONCLUSION: The study results indicated that higher NISS correlated to longer HLS, fewer home discharges, and increasing mortality. Specialized hospitals for TA patient rehabilitation are necessary to reduce disabilities in TA patients.