Run-off-road (ROR) incidents on curves, as one of the most accident-prone locations on roads, have always attracted special attention. Centrifugal force exerted on vehicles and human error are considered two fundamental factors in accident occurrence in these areas, ultimately leading to vehicle rollover or skidding. Rollover and skidding of SUV vehicles are among the critical parameters in the issue of vehicle deviation on curves, and according to accident statistics, they are associated with significant human and financial losses.The importance of enhancing safety on downgrades is amplified, especially on mountainous routes, due to the potential combination of horizontal curves with vertical alignments and/or their combination with so-called steep grades. The AASHTO guideline, as the most reputable road design manual, uses the "point mass model" to define vehicle behavior when traversing curves. This, in effect, means excluding the principles of physics and mechanical engineering from road design, which consequently leads to reduced safety. One of the fundamental limitations of the point mass model is its disregard for the differential force distribution on the vehicle's various wheels and axles. The final results of this research indicate reduced safety on curves and bends with steep foreslopes (1:3 and 1:4). To address this issue, the present study provides new relationships for use in road design.