EVALUATING THE GEOMETRIC DESIGN CONSISTENCY AND ROAD SAFETY ON TWO-LANE SINGLE CARRIAGEWAYS USING OPERATING SPEED CRITERIA

*Igene, M. O.  & Ogirigbo,  O.  R.

Department of Civil Engineering

                                                                                                  Faculty of Engineering

University of Benin, P.M.B. 1154, Benin City, Nigeria

Email: morris.igene@uniben.edu

*Corresponding author

ABSTRACT

This work focuses on two-lane single carriageways that contain sections, which make transition from one geometric feature to another unsafe, and thereby resulting in driving errors that may eventually lead to driving off course and accidents. The two-lane single carriageway selected for the study was the Ekiadolor-Olumoye-Uhen road, a rural highway in Edo State, Nigeria. Alignment data such as curve radius, length of curve, beginning and end point of curve, as well as vertical slope, were obtained from satellite imageries using Geographic Information System (GIS); while the operating speed reduction (∆V₈₅) between tangents and curves was estimated at various sections of the selected route. These data were used as input parameters in generating an Accident Prediction Model. The model was generated using the Generalized Linear Regression Modelling (GzLM) approach. The results obtained from the study showed that the curves between sections 11.4 – 11.9km, 21.5 – 22.0km and 24.0 – 24.5km, fell slightly short of the criteria of a good design and therefore required warning signs to be placed before the transitions; whereas the curves between sections 16.8 – 17.4km and 26.6 – 27.8km, fell very short of the criteria of a good design, and were classed as poorly designed.

Keywords: Consisten cy, Operating Speed, Geometric Design, Rural Highway, Accident Prediction Model.