Lateral Placement Behaviour along Horizontal Curve Sections under Mixed Traffic: Evidence from North Easter Hill range of India

Abstract

Vehicle lateral placements reflect how drivers negotiate horizontal curves and may have influence on roadway operation and safety performance. This paper examines vehicle lateral placement behavior on a four-lane mediandivided hilly highway. Lateral placement was measured at three gates, namely the entry, center and exit, on ten horizontal curves of the Itanagar–Naharlagun section of NH-415, yielding 26,898 vehicle observations. Each gate was analyzed on its own, and the spread of placement at each was fitted to a scaled Beta model built from the measured mean and variance. The section effect was then tested twice. Averaged over the ten curves, the Friedman test showed no statistically significant section effect for any class; such averaging washes out the very within-curve movement that the study set out to capture. With the same vehicle followed through all three gates, a matched Friedman test made the section highly significant for every dominant class, namely car, SUV, motorcycle and scooter, with p below 0.001 throughout. Its shape did not change from one class to the next. Vehicles ran widest near the center and drew closest to the median at the exit, a swing of barely 0.2 to 0.4 m. The section therefore shifts placement in a reliable but small way, and accounts for only a modest part of the overall spread. The results show section specific evaluation of horizontal curves indicate that driver lateral position behavior varies between entry center and exit section