EVALUATION THE EFFECTS OF GEOMETRIC DESIGN PARAMETERS ON TRAFFIC CRASHES(A CASE STUDY: ALETA WONDO - BONA DAYE ROAD SECTION)

Abstract

The problem of road crashes have been increasing in alarming rate and it is a serious problem all over the world, mainly in developing countries. Ethiopia‟s road accidents in terms of volumes, frequencies and severities are among the highest in the world. Specifically in Ethiopia,Sidama Zone under SNNPR has taken as one of leading road traffic crashes, particularly on Aletawondo - Bona - Daye road section. The objective of this study was to investigate the effect of road geometric design elements on road traffic crash occurrences at road segments on Aletawondo-Bona-Daye road section. In this study, data were collected regarding geometric characteristics; the number of crashes and traffic volume from twenty-nine (29) road sections which were selected based on the convenience sampling method. A total of 203 number of road accidents were collected from the woredas, Alatawondo and Daye town and Sidama Zone Police Commission over a period of five years, between 2013/14 and 2018/19. Regarding the analysis of the data, the Poisson Regression model and the Negative Binomial Regression models and Empirical Bayesian (EB) methods were utilized. The SPSS 20 software packages were applied to analyze the effects of variables. In addition to this, descriptive statistics was used to conclude the nature and characteristics of crash occurrences. A sum of 331 road crash data was gathered for five consecutive years comprising 47 fatal, 143 injuries and 141 property damages only for the general analysis in the study road section. The results of this study showed that there is a strong correlation between road geometric design elements and road crash occurrences. The modeling result indicated that gradient, median type, number of horizontal curves, number of vertical curves, number of lanes, sidewalk or shoulder width, number of access, number of access controls and average daily traffic are significantly affecting road crash occurrences. The general analysis in the road section reveals that most crashes occurred at road sections, painted two-way and one-way roads, particularly in rural residential and non-residential (forestry) areas. The EB result indicated that among 29 studies road sections, 13 sections were highly prone to accidents with PI values. The results of this study envisaged to support transport planners and road designers in consideration of road safety issue and sustainable road design standards and giving technical awareness for traffic policy on traffic data