The determination of the geometric vehicle movement is significant for the appropriate design of a road element, such as an intersection or a parking lot, because it ensures safe, smooth and without abrupt changes movements especially for heavy vehicles. Consequently, the accurate and correct swept path analysis of the vehicles determines the geometry of the horizontal alignment. Also, the selection of the design vehicle is a factor that affects the geometric characteristics of the analysis. The AASHTO Green Book presents the minimum turning paths, the maximum steering angle and the minimum centerline turning radius (CTR) for typical design vehicles. In order to simplify the geometrical problem of swept path analysis, the speed in sharp curve road is considered to be low and more specifically less than 15 km/h. However, this condition does not represent the actual vehicle movement, gap that the present paper aims to bridge by performing swept path analysis for increased travel speeds. There are only few cases, especially along urban road network that the lateral force applied on the vehicles that traverse horizontal transition curves are neglected due to low travel speed. On the contrary, in other road projects the transition curve is an integral design element and have advantages in geometric regularity of heavy vehicles movement because of their steering mechanism. Based on the literature review, in this study the design vehicles paths which are considered as clothoid shapes are correlated with their corresponding travel speeds. The implemented methodology considers various design vehicles which travel in various speeds, performing U-Turns.
A STUDY ON AGRICULTURAL TRACTORS STEERING MECHANISM 2- The turning radius 3- Deviation of the turning center (DTC)
