Operating Speed of Different Classes of Vehicles at Horizontal Curves on Two-Lane Rural Highways

The majority of operating speed models reported in the literature primarily consider passenger cars and only rarely consider heavy vehicles. No study on the influence of geometry on speeds of other classes of vehicles like buses and two-wheelers, which contribute significantly to the mix of traffic in India, has been reported. This study highlights the need to develop operating speed and speed reduction models for different classes of vehicles and develops models for predicting operating speed at tangent and midcurve sections of horizontal alignment of two-lane rural highways. In addition, models for estimating the speed reduction from tangent to curve are also developed. The independent variable used to predict tangent speed is the length of the preceding tangent. The radius and length of a curve emerged as the most important variables for speed at midcurve. Speed reduction can be estimated from the preceding variables along with the approach tangent speed. The models developed in the study can be used in the design and evaluation of rural highways as well as in establishing speed limits and other enforcement measures.

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