Risk-based design of roadway crossing structures considering intangible factors

The least total expected cost (LTEC) design frequency is the conventional, solely economically-based design frequency using tangible factors, while the extended-LTEC design frequency considers other intangible factors in the determination of flood design frequency for highway drainage structures. The risk-based design used to study these design frequencies considers the inherent hydrologic uncertainty in calculating the expected economic losses. The design frequency is a decision variable rather than a pre-selected design parameter as in the traditional design procedure. In the analysis, the annual expected flood damage cost should be the incremental damage as the result of the presence of the roadway crossing structures.