Road and Transportation Engineering

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Browsing Road and Transportation Engineering by Subject "85 th percentile speed"

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    Exploring the Causes of Traffic Crash and Injury Severity on Addis Ababa - Adama Expressway
    (Addis Ababa University, 2022-06) Bedria, Hussien; Getu, Segni ()PhD)
    Road traffic crashes is a serious problem since it increased periodically in alarming rate throughout the globe. It is the eighth leading causes of death for all age groups worldwide, especially in developing countries. According to the global status report on road safety, in Ethiopia, road traffic deaths occurred about 26.7 per 100,000 populations. The objective of the study was to explore the causes of Traffic Crash and Injury severity on Addis Ababa - Adama Expressway. In the study, eighteen main variables (with sixty two sub variables) are derived from the three major contribution factors of roadway environment, human and vehicle factors. For the analysis, five years (from July 8, 2016 – July 7, 2021) recorded traffic crash data and traffic flow data taken from Ethiopian Toll Roads Enterprise and the as-built drawings of the expressway taken from Ethiopian Roads Authority. During the last five-year study period, a total of 1838 traffic crash occurred on the expressway causing 98 (4.0 %) fatal injuries, 268 cases (10.94 %) serious injuries, 700 cases (28.57 %) slight injuries, and 1384 cases (56.5 %) were property damage only (PDo). Descriptive Statistics and empirical statistical analysis by ordered logistics regression model was carried for the analysis of traffic crash and severity. Moreover, the operating speed of vehicles and 85 th percentile speeds of each type of vehicle category is computed to compare and evaluate the daily number of vehicles exceeded the posted speed limit of the expressway. The analysis result show that, among the sixty two independent variables, seventeen independent variables are statistically significant with p-value of <0.05 with 95 % Confidence Interval and they have significant influence on accident severity. These influencing variables include; radiuses of horizontal curves in the range of 61m - 120m and 251m – 900m, level grade (0%), downgrade, light vehicles, medium vehicles, vehicle technical problem, speeding, sleep deprivation and fatigue, drivers error, head on crash, rear-end, roll over, sideswipes collisions, weekdays , driver’s age from 18 – 30 and 31 - 50 yrs. are statistically significant for the severity of crash on the expressway