Three-Dimensional, Probabilistic Highway Design

Abstract

The potential usefulness of reliability analysis has recently been stressed in many engineering applications. Given the variability in the design parameters, a reliability-based probabilistic approach is well suited to replace the current deterministic highway design practice. However, progress in this regard is generally slow. In this study, the reliability analysis was used to estimate the probability of hazard (POH) that might result from insufficiency of sight distances. As an application, the available sight distance was checked against required stopping sight distance on an assumed road segment. Variation of the design parameters was addressed with Monte Carlo simulation using 100,000 sets of design parameters based on distributions available in the literature. A computer program was developed to use these sets of design parameters to calculate the profiles of available and required stopping sight distances in two- and three-dimensional projections as well as the profile of POH. The approach was applied to a horizontal curve overlapping with flat grade, crest curves, and sag curves in a cut section where the side slope would restrict the sightline. The analysis showed that the current deterministic approach yields very conservative estimates of available and required stopping sight distance, resulting in very low POH. The application example also showed the change of POH with the change of vertical alignment parameters.

Evaluation of 3D coordination to maximize available stopping sight distance in two-lane rural highways

“…3D methods are more accurate on sight distance evaluation despite the difficulty on their development. Graphical (Sanchez 1994), finite element (Castro et al 2014;Hassan et al 1996;Hassan, Easa 1998;Ibrahim et al 2012;Jha et al 2011;Romero, Garcia 2007;Yan et al 2008) and analytical (García 2004;Ismail, Sayed 2007;Lovell et al 2001;Kim, Lovell 2010;Sarhan, Hassan 2008 approaches were studied by others. However, only the finite element methods were applied to optimize available sight distance .…”

Reliability-Based Safety Evaluation of Headlight Sight Distance Applied to Road Sag Curve Standards

“…Among the different reliability analysis methodologies, Richl and Sayed [31] applied the FORM and SORM to determine the risk associated to narrow medians combined with horizontal curves in stopping maneuvers using the Reliability Analysis Software (RELAN). Sarhan and Hassan [32] used the Monte Carlo sampling method to verify the SSD in 3D alignment combinations of horizontal curves in a cut section, where the cut side slope restricted the sight lines.…”

Performance-Based Analysis in Civil Engineering: Overview of Applications

“…Various applications related to geometric design and traffic operations [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] are found in Table A1. The applications rely mostly on the geometric design guides by AASHTO [35] and the Transportation Association of Canada (TAC) [36].…”

“…El-Khoury and Hobeika [23] applied MC simulation to estimate the uncertainty level contained in passing sight distance (PSD) requirements on straight roadway segments. A reliability-based design method was developed to estimate the uncertainty of the three-dimensional (3D) SD boundaries on horizontal alignments that overlap with flat grades, crest curves, and sag curves [24]. For the horizontal alignment of two-lane rural highways, Easa and Mehmood [25] developed a substantive-safety approach based not only on minimum design guidelines, but also on actual collision experience.…”