Use of Risk Analysis to Minimize Adverse Consequences in Nonstandard Designs

Roadside safety engineers lack a quantitative method to balance the philosophies presented in AASHTO's Roadside Design Guide (RDG) with situations encountered on existing roads, especially where it is not possible to follow the guidelines in the RDG. In general, the goal of roadside design is to minimize, insofar as is practical, the chances of severe or fatal injury crashes on the roadway. Engineers are often left to use good engineering judgment to make these choices. This paper presents a risk assessment methodology and demonstrates through example problems how this methodology may be used as a more quantitative approach for measuring the inherent risk of roadside design alternatives so that engineers can identify where the greatest safety benefit can be realized. Benefit–cost methods have been used in roadside safety for more than 35 years to balance improvements in safety with implementation costs. Although the methods have been widely used, the approach has presented several challenges. This paper discusses the advantages and challenges of the use of the benefit–cost method and the proposed risk method. The two tools can be used together for better roadside designs and policy.