Case study of superelevation design at an expressway interchange by using ADSCivil Road software

Superelevation is known as a transverse slope made available to mitigate the impact of centrifugal force and minimize the vehicle's tendency to overturn and skid. However, in an intersection or interchange that has horizontal curves with small radius consecutively, it is difficult to design superelevation. If the superelevation arrangement is not good enough, the alignment is not smooth, causing unfavourable and unsafe conditions. Moreover, for expressway interchange, it become more complicated to design by manual method because the expressway requirements in term of safety and aesthetics is higher than that of conventional intersection. On the other hand, ADSCivil Road, a software in the ADSCivil solution suite for infrastructure design developed by Baezeni Soft Co, Ltd. is a useful tool for geometric road design. This paper presents the results of ADSCivil Road software application in designing the superelevation at the expressway. ADSCivil Road has arranged superelevation for an interchange ramp (with a design speed of 60 km/h) that includes the small radius circular curves connecting together (R=125 m and R=100 m). The results show that using the superelevation diagram and corridor model in ADSCivil Road makes the superelevation design process more intuitive, make it easier to adjust the slope at each point, and controls the rate of superelevation difference. In addition, ADSCivil Road automatically updates the superelevation change for profile, cross-section and plan. Also, 3D simulation results show that the superelevation layout for this interchange meets technical, economic, and aesthetic requirements. Obviously, it can be seen that can become an effective tool to help engineers solve complex problems in road design.