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Lookup NU author(s): Ibrahim Hashim,
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Improving road safety is a high priority for highway authorities. It is believed that geometric design consistency may affect road safety on rural single carriageways, which exhibit higher accident rates than other rural roads. This research aims to study the geometric consistency and safety of rural single carriageways, many of which follow historic alignments, and are not designed to modern standards. This paper investigates the operating speed and geometry relationships for rural single carriageways using speed data collected for curves and tangents in two counties in the North East of England. Accurate operating speed models are needed to calculate the measures of Geometric Design Consistency. They include models for curves, straights and acceleration/dec eleration behaviour prior to or following the curves/ straights. A series of speed surveys were carried out in the North East of England. A novel method of estimating horizontal curvature details from digital mapping was developed for this study. Other geometric features of the survey sites were measured on site using appropriate electronic and manual methods. Analysis of the spot speed distributions confirmed the findings of previous research, following a normal distribution in the majority of cases. Significant differences were found between the mean and operating speeds in the two directions of flow. Further analysis looked at the differences between speeds on the inside and outside of curves. Single and multiple regression analysis were used to examine the speed data and the various geometric parameters of tangents and curves to find suitable operating speed models. The best predictive models for curves were found to rely mainly on the radius of the curve. On tangents the speed was mainly dependant on the length of the tangent.
Author(s): Hashim IH, Bird RN
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Unknown
Conference Name: 37th Annual Conference, Universities’ Transport Study Group
Year of Conference: 2005