RECOMMENDATIONS FOR EVALUATING HORIZONTAL DESIGN CONSISTENCY BASED ON INVESTIGATIONS IN THE STATE OF NEW YORK

To a large extent, critical driving maneuvers on two-lane rural highways can be related to vehicular speeds that are inconsistent with the roadway alignment presented to the motorist. A method for identification of horizontal alignments that create speed transition problems for the motorist and recommendations for correcting them, for example, through the resurfacing, restoration, and rehabilitation (RRR) program, may help to improve highway safety on this important portion of the road network. An analyis based on design, speed, volume, and accident data for 261 road sections of two-lane rural state routes in the state of New York established (a) the relationship among the German design parameter curvature change rate, the American design parameter degree of curve, and operating speeds of passenger cars for different lane widths; (b) the effect of additional design parameters and volume data on operating speeds; (c) the relationship between degree of curve and accident rate for all lane widths and vehicle types; (d) estimates of reasonable ranges of degrees of curve and the corresponding operating speeds for good, fair, and poor designs; and (e) recommendations for evaluating critical inconsistencies in horizontal alignment. By applying these recommendations, the highway engineer could control minor inconsistencies in highway alignment, and detect and correct major geometric defects, for example, in conducting RRR projects.