A new approach to optimizing the radius of the horizontal curves of the country's military roads

In Iran, the Code 415 is used to study the geometric design and road safety. There are no specific manuals to design military roads. This paper is aimed to optimally design the radius of horizontal curves in military roads under more realistic conditions. For the purpose of road geometric design in the Code 415, the minimum radius of horizontal curves is calculated based on the point mass model. In the real world, vehicles move like a multi-dimentional mass not a rigid one, therefore the equation presented in the code 415 can be questioned. This doubt seems to be reasonable, since in reality, the forces acted on each single tire differes as vehicle passes the horizontal curve. So, in order to analyze more accurately, 112 scenarios are considered in this research. The scenarios include different slopes, grades, rollover indices, load transfer indices, lateral friction factors in the horizontal curves. The results showed that considering the dynamic limitations of lateral acceleration, Rollover index, load transfer index, Roll rate, lateral friction factor, the proposed radius in this paper can be lower than the proposed radius in 415 by 95.6 percent. These proposed radii of of horizontal curves are suitable and widely used in difficult operational-military routes.