Road traffic crashes is a serious problem since it increased periodically in alarming raternthroughout the globe. It is the eighth leading causes of death for all age groups worldwide,rnespecially in developing countries. According to the global status report on road safety, inrnEthiopia, road traffic deaths occurred about 26.7 per 100,000 populations. rnThe objective of the study was to explore the causes of Traffic Crash and Injury severity onrnAddis Ababa - Adama Expressway. In the study, eighteen main variables (with sixty two subrnvariables) are derived from the three major contribution factors of roadway environment,rnhuman and vehicle factors. For the analysis, five years (from July 8, 2016 â€“ July 7, 2021)rnrecorded traffic crash data and traffic flow data taken from Ethiopian Toll Roads Enterprisernand the as-built drawings of the expressway taken from Ethiopian Roads Authority. Duringrnthe last five-year study period, a total of 1838 traffic crash occurred on the expressway causingrn98 (4.0 %) fatal injuries, 268 cases (10.94 %) serious injuries, 700 cases (28.57 %) slightrninjuries, and 1384 cases (56.5 %) were property damage only (PDo). rnDescriptive Statistics and empirical statistical analysis by ordered logistics regression model rnwas carried for the analysis of traffic crash and severity. Moreover, the operating speed ofrnvehicles and 85rnthrn percentile speeds of each type of vehicle category is computed to comparernand evaluate the daily number of vehicles exceeded the posted speed limit of the expressway. rnThe analysis result show that, among the sixty two independent variables, seventeenrnindependent variables are statistically significant with p-value of