GEOMETRIC DESIGN CONSISTENCY BASED ON SPEED CHANGE ON HORIZONTAL CURVES

This paper proposes a methodology for identifying and evaluating horizontal alignment consistency based on the analysis of speed reduction on horizontal curves. The paper also investigates the effects of a number of geometric design elements on operating speeds. It was found that the reduction in the 85th percentile speed on curves with long approach tangents is strongly correlated with both degree of curvature and curve deflection angle. A speed reduction model is developed and applied to compare two alternative horizontal alignments of a proposed rural highway in Jordan. It is recommended that existing minimum radius requirements, such as those of AASHTO, be extended under certain circumstances, to achieve consistency in horizontal alignments. (a)