Designing the Highway for the Vehicle

The major difficulty facing the highway designer of today is the lack of a formal design procedure. Unlike the more organized engineering approach, wherein a design is developed from first prin­ ciples and then tempered by experience, the highway engineer relies almost entirely upon prior knowledge. Thus, we have the “gradeseparation” expert, the “drainage man,” the “intersection designer,” the “traffic engineer,” and so forth, each of whom is a specialist able to reproduce his given speciality based on accumulated experience. This situation is not new. The history of engineering is replete with similar examples, as witness the coefficients of the hydraulics people prior to the formulation of fluid, mechanics, the “code” expert who pre-dates soil mechanics, and others. In each area, rule-of-thumb methods prevailed until the advent of a more scientific approach.