A simulator approach to study the effect of spiral curves on driver's behavior for two-lane rural highway

Many studies based on spot locations have been conducted to improve highway design consistency to reduce accident rates. Traffic accidents had a strong relationship with environmental sustainability in terms of emissions and natural resources consumption. This study based on driving a simulator can produce continuous drivers' behavior profiles to facilitate analyzing the behavior on various curves' scenarios (with/without spiral). This paper studied the effect of the spiral transition curves on drivers' behaviors in terms of speed and lateral position with changing geometric features of horizontal curves at the two-lane rural highway. Seventy-two participants were selected to ride on 48 different curves. Curves of experimental track had 4 radii, 3 deflection angles, 2 directions and with/without spiral. Drivers' speed behavior studied at five specific locations at every curve, and 3 segments at studying the lateral position. Effect of spiral studied according to 3 approaches; changing radius, deflection angle, and direction of the curve. Briefly, spiral had significant in small radii curves and sharp deflection angles by increasing the average speed at curves and reduced tangent-to-curve speed reduction. Also, spiral decreased the lateral displacement at approach tangent and during the curve