To improve design consistency, several studies developed operating speed prediction models and investigated drivers’ speed behaviour. Most of the existing models are based on spot speed data assuming constant operating speed throughout the horizontal curves and occurrence of acceleration and deceleration only on tangents. To overcome limitations associated with these hypotheses, this study investigated continuous speed profiles by a driving simulator experiment carried out on a two-lane rural highway using the VERA high-fidelity dynamic-driving simulator. A piecewise linear regression model and locally weighted regression scatterplot smoothing were used to remove the noise in the data set while preserving underlying patterns and to identify the significant changes in the speed profile. Based on the smoothed speed profiles, models to predict operating speed in curves and in tangents, deceleration and acceleration rates to be used in the operating speed profiles, and starting and ending points of constant operating speed in curve were developed. Notably, radius of the curve affects not only the operating speed in the curve but also the operating speed of the tangent following the curve. The smaller the radius, the lower the operating speed on the exit tangent. Both acceleration and deceleration rates increase with curvature, which is the reciprocal of radius. An important result of our study is that the operating speed is not constant along the curves. On small radius curves, deceleration ends close to the center of the curve and acceleration starts close to the end of the curve. Increasing the curve radius, the endpoint of deceleration moves towards the beginning of the curve whereas the acceleration beginning moves towards the center of the curve. Conversely, and also noteworthy, the speed differential between an approach tangent and a horizontal curve (tangent-to-curve speed differential), the consistency measure with the greatest safety effect, is higher when long tangents are preceded by curves with large radius.

Continuous Speed Profiles to Investigate Drivers' Behavior on Two-Lane Rural Highways / Montella, Alfonso; Galante, Francesco; Mauriello, Filomena; Aria, Massimo. - In: TRANSPORTATION RESEARCH RECORD. - ISSN 0361-1981. - 2521:(2015), pp. 142-154. [10.3141/2521-01]

Continuous Speed Profiles to Investigate Drivers' Behavior on Two-Lane Rural Highways

MONTELLA, ALFONSO;GALANTE, Francesco;MAURIELLO, FILOMENA;ARIA, MASSIMO
2015

Abstract

To improve design consistency, several studies developed operating speed prediction models and investigated drivers’ speed behaviour. Most of the existing models are based on spot speed data assuming constant operating speed throughout the horizontal curves and occurrence of acceleration and deceleration only on tangents. To overcome limitations associated with these hypotheses, this study investigated continuous speed profiles by a driving simulator experiment carried out on a two-lane rural highway using the VERA high-fidelity dynamic-driving simulator. A piecewise linear regression model and locally weighted regression scatterplot smoothing were used to remove the noise in the data set while preserving underlying patterns and to identify the significant changes in the speed profile. Based on the smoothed speed profiles, models to predict operating speed in curves and in tangents, deceleration and acceleration rates to be used in the operating speed profiles, and starting and ending points of constant operating speed in curve were developed. Notably, radius of the curve affects not only the operating speed in the curve but also the operating speed of the tangent following the curve. The smaller the radius, the lower the operating speed on the exit tangent. Both acceleration and deceleration rates increase with curvature, which is the reciprocal of radius. An important result of our study is that the operating speed is not constant along the curves. On small radius curves, deceleration ends close to the center of the curve and acceleration starts close to the end of the curve. Increasing the curve radius, the endpoint of deceleration moves towards the beginning of the curve whereas the acceleration beginning moves towards the center of the curve. Conversely, and also noteworthy, the speed differential between an approach tangent and a horizontal curve (tangent-to-curve speed differential), the consistency measure with the greatest safety effect, is higher when long tangents are preceded by curves with large radius.
2015
Continuous Speed Profiles to Investigate Drivers' Behavior on Two-Lane Rural Highways / Montella, Alfonso; Galante, Francesco; Mauriello, Filomena; Aria, Massimo. - In: TRANSPORTATION RESEARCH RECORD. - ISSN 0361-1981. - 2521:(2015), pp. 142-154. [10.3141/2521-01]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/614857
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