Risk‐Cost Design of Pavement Drainage Systems

Abstract

A practical method for determining the road surface drainage system design with the theoretical lowest total economic cost (LTEC) is developed. The LTEC method determines the design rain which, when used in a rational‐based design context, will yield the most economic choices of gutters, inlets, and laterals considering both construction costs and risk costs. The method provides an alternative to the use of fixed return period design criteria. Daily rainfall serves as the random variable used in performing the risk analysis. The right‐hand tail of the probability density function for daily rainfall is approximated with a normal curve. A triangular hyetograph of average duration is assumed to be appropriate for representing an individual rainstorm. A nomograph and data selection guide are provided as design aids. Case studies are presented in an appendix. The method, based on minimizing traffic delay costs, applies to freeways, arterials, and major collectors; local streets with low traffic may be excluded.