The program implements the methodologies detailed in the manuals of the Federal Highway Administration (HEC-12 for drainage of highway pavements and HEC-21 for bridge deck drainage) for the design of storm water inlets. Computation of runoff is based on the Rational Formula. The major advantage of this program, as compared with other inlet design programs already available, is that the profile grade of the bridge or pavement is automatically computed for every point within the specified design limits. The program also allows the user to automatically vary the cross-slope for superelevated sections, and to include the flat bridge algorithm (HEC-21) in the design and analysis.
The MPADD2 program is based on the 1984 version of the "Pavement Drainage" (PD) computer program developed by Fred Chang for the Federal Highway Administration. The program expands the capabilities of the PD program and simplifies the design procedure for the user. The tasks are selected from menu bars and dialogue boxes. An input file is created or edited in form that simulate pages in a folder, and help windows are available for guidance regarding each decision to be made in the process. Input data can be changed in the form and analyzed quickly to obtained the desired design without create additional input file.
A graphic display of the profile grade and selected inlet locations (along with the discharge and spread information) allows the user to visually inspect the completed design. Utility programs have been added for calculating the profile grade, drainage area properties, spread, inlet capacities and flat bridge inlet spacing. The program format provides for a simple, efficient and accurate design procedure. Changes in inlet type or location can be made easily by use of the edit capabilities of the program.