The aim of this study was to find an up to date operating speed model for rural single carriageways (two-lane highways) in the United Kingdom, as part of wider research into the consistency of highway alignment. A series of speed surveys were carried out in the northeast 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 analyses 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 dependent on the length of the tangent.
Samenvatting