Risks of Unprotected Median Drainage Ditches on Vehicle Stability

In this study, potential risks of unprotected triangular and trapezoidal cross-sectional median drainage ditches on vehicle stability was investigated. Dynamic simulations were carried out to determine the safety concerns and suggest appropriate countermeasures. Drainage structures geometry, characteristics of vehicles entering the ditches, vehicle approach angle and velocity were described as variables for the analysis. Finite element analysis program LS-DYNA was used to simulate the dynamic interaction between vehicle and ditch. Based on the analysis results it was determined that vehicles tend to either: (a) rollover or enter opposing lanes in an uncontrolled manner or (b) remain inside the ditch when the velocity and encroachment angle is low. To provide the required level of safety and security at drainage ditches, use of guardrail was also investigated. Based on the crash simulations, it was concluded that when guardrail location is correctly selected the H1-level guardrail provided acceptable performances with respect to vehicle stability.