Application of System Reliability Analysis in Geometric Design: A Case Study of Horizontal Curves on the Sea to Sky Highway

Existing geometric design guides provide a deterministic approach for design requirements using conservative percentile values of design inputs to account for the uncertainty associated with these inputs. Recently, researchers have advocated the use of reliability analysis to account for uncertainty in the geometric design process and to evaluate the risk associated with a particular design. In this approach, a risk measure (e.g., probability of noncompliance) is calculated, representing that a specific design would not meet standard requirements. Most applications of reliability analysis in geometric design focused on evaluating the probability of non-compliance for one particular design feature such as the sight distance (e.g. available sight distance (ASD) is less than the required stopping sight distance (SSD)). However, in many design situations, non compliance may be present due to more than one design feature (e.g. insufficient sight distance and vehicle skidding). In these situations, the series system reliability approach which considers more than one failure (non-compliance) modes needs to be used. The main goal of this paper is to demonstrate the application series system reliability analysis to highway design problems. The process is demonstrated through a case study for the design of horizontal curves. Two non compliance issues are considered including limited sight distance and vehicle skidding. The results show the importance of accounting for several design features in the reliability model. System reliability could be used in future studies to calibrate the design of horizontal curves in order to achieve consistent safety levels based on all possible modes of failure.