# A Unified Approach for Risk Assessment of Road Crash Barriers Using Bayesian Statistics
## 2 Research on Current Scientific Knowledge  
The topic of road safety, specifically road safety inspections, as well as other approaches to assessing the level of safety of the transport space, has been addressed by a number of domestic and foreign research studies. Some possible examples include a study from Alabama, USA, that assessed the influence of risk factors in relation to the severity of injuries caused by crashing into a crash barrier (i.e., vehicle detention, vehicle redirection, and barrier breach). A total of 1685 crash barrier accidents that occurred on three major international highways over a seven-year period (2010-2016) were analysed. Aspects of the barrier (e.g., central reservation width, barrier length, barrier offset, and lateral location) were assessed. Two types of longitudinal barriers were analysed: high tension cable barriers installed in the central reservation and fixed post barriers installed in the central reservation or soft shoulders. Separate mixed logit models (MXL) were used to analyse crash injuries, assessing the severity of crashes related to barrier impacts and estimating injury consequences. The MXL models were able to identify factors that contributed to crash severity and consequences of crashes with crash barriers. Recommendations were made that crash barriers longer than 0.2 miles (322 m) should be implemented to reduce the probability of barrier breaches and reduce the number of crashes with these consequences [21]. Another example is a study explaining human biomechanics in relation to guardrail intrusion into a vehicle's crew cab. At the same time, the study evaluates the biomechanical effectiveness of hybrid tensile compression guardrails for better passenger protection. Nine fatal crashes with guardrail intrusion into the vehicle were analysed. Four crash tests between cars and crash barriers were performed using a hybrid guardrail that integrated a commonly used W-beam with a new tension-based end section design. The test involved the impact of a platform colliding with small vehicles (sedan, pick-up) at highway speed. The impact orientation was varied to simulate frontal and curve impacts with speeds ranging from 90 to 111 km/h. Studies showed that fatal injuries were caused by guardrail impalement regardless of vehicle speed and size. Passengers who were not in the trajectory of the guardrail in the same vehicle sustained minor injuries despite experiencing similar energy levels. In these cases, the impact intensity was survivable. The average pre-impact speed, change in speed, and acceleration of the vehicle were 117 km/h, 20 km/h, and 97 m.s\({}^{-2}\), respectively. The hybrid guardrail system deflected the vehicle without any intrusion into the passenger compartment. The average peak accelerations in the crash tests were below the injury thresholds. Research shows that the hybrid guardrail system not only eliminated intrusion into the passenger compartment for survival of the crash, but it also deflected the vehicle off the collision course [22]. Vehicle collision research with bridge crash barriers was presented in a study that focused on a new type of prefabricated crash barrier. This restraint system was assessed using LS-DYNA, a nonlinear imaging dynamic analysis program, and numerically analysed models of vehicle collisions with this type of crash barrier were developed. Subsequently, a time curve of the energy distribution during the vehicle collision was generated. Based on the developed model, the collision process of the vehicle with the installed anti-collision crash barrier was analysed. The result shows that the assembled anti-collision crash barrier proposed in this article can better change the trajectory of the moving vehicle and can prevent the vehicle from falling off the bridge. The collision results show that the assembled anti-collision crash barrier for bridges proposed in this article can reduce vehicle damage and effectively protect the driver.