Acceleration and Deceleration Patterns on Horizontal Curves and Their Tangents on Two-Lane Rural Roads

Abstract

Acceleration/deceleration patterns most commonly used by drivers are necessary to develop the speed profiles for road geometrical design and consistency assessment. Typically, an acceleration/deceleration value of 0.85 m/s2 is used. The state of the art shows that this value differs from those obtained through direct measurement. Therefore, it is necessary to improve the models for estimating the acceleration/deceleration values. This paper presents a study of the acceleration/deceleration patterns of light-weight vehicles measured on three two-lane rural roads in Argentina. These values were measured using a GPS logger and a high resolution camera mounted on the cars used in the experiment. The work studied three aspects, namely, the deceleration on the approach tangent to horizontal curves, the deceleration along the horizontal curve, and the acceleration on the exit tangent. Data were collected at 386 horizontal curves having radii shorter than 1,000 m, with approach and exit tangents measuring up to 400 m and longitudinal slopes below 5%. In the experiences, data were measured for experiences with 9 drivers, who completed up to 12 runs per curve. The experimental results show that the acceleration/deceleration rates follow a Burr’s probability density function. It was found that the deceleration values obtained are not constant along the tangents and curves, and that they are strongly dependent on the available length of the approach tangent, on the radius of the curve and the longitudinal slope. The accelerations obtained depend mainly on the available exit tangent.