PAVDRN is a computer model that determines the speed at which hydroplaning will be initiated on a section of highway pavement. It is intended to be used by highway engineers before final geometric design to (a) indicate the location of the worst incidence of hydroplaning that is likely to occur on a given section and (b) to rapidly assess different geometric configurations of a section and pavement materials to select a design that will minimize hydroplaning potential. The model is based upon a one-dimensional, steady-state form of the kinematic wave equation. This equation is used in conjunction with relationships for Manning's n that account for the nature of the shallow flow over highway pavements. Ultimately, water-film thickness along a maximum flowpath length is used in empirical expressions to determine the speed at which hydroplaning is likely to occur along this path. The path is determined by analyzing the geometry of the pavement section. Five different geometric sections can be analyzed: ( a) tangent section, ( b) superelevated curve, ( c) transition section, ( d) vertical crest curve, and ( e) vertical sag curve. The user interface was written in Microsoft Visual Basic Version 3.0. It uses context-sensitive help screens. The algorithms for water-film thickness and hydroplaning potential were written in FORTRAN 77.