Longitudinal Acceleration Models for Horizontal Reverse Curves of Two-Lane Rural Roads

Abstract

The operating speed profile models adopt acceleration and deceleration as constant values obtained from kinematic models, assuming that the operating speeds between two consecutive sections are not spatially correlated. Existent research shows that acceleration and deceleration in horizontal reverse curves (HRC) depend on the tangent length and curve radii. In this paper, accelerations/decelerations-geometry models for light cars are proposed. The models are based on the data obtained in-field with a 10 Hz GPS under favourable traffic, weather, and pavement condition to isolate the effect of road geometry over the speed changes. The models were calibrated using the 95th percentile of acceleration probability density function (pdf) obtained section to section in the HRC. It was found that the acceleration and deceleration pdf follow the Burr distribution. Therefore, a Box–Cox transformation is needed to properly calibrate acceleration-geometry models. The models obtained confirmed that accelerations and decelerations depend on the radius of entrance and departure curves of the HRC. The results contribute to better understanding of the acceleration/deceleration patterns of light cars and to enhancing operating speed models in the HRC.

Keywords

• acceleration/deceleration rate
• horizontal reverse curves
• light cars
• longitudinal acceleration-geometry models
• two-lane rural highways