DARWin is the designation for and represents the series of AASHTO's computer software programs for pavement design and is an implementation of the 1993 AASHTO publication - Guide For The Design of Pavement Structures.

DARWin 3.1 is a metric-compliant AASHTOWare computer software product that conforms to and is compliant with the pavement design models presented in the respective design guide documents. However, DARWin allows the pavement design engineer to accomplish much more. For example, in flexible pavement design, DARWin allows the calculation of layer thickness by three user-selected methods, including an optimization scheme. Rigid pavement design is enhanced by the addition of the steel design equations for JRCP and CRCP and by the inclusion of in-depth guidance on many of the inputs to the rigid pavement design equation. The overlay design module incorporates the revised approach to pavement overlay design developed under NCHRP Project 20-7. The overlay design module provides a fully automated means of performing all of the different overlay design calculations, including automated FWD file processing and back calculation.

The module on life-cycle costs in DARWin is designed so that the user can input costs in the same format as they are made available for initial construction, rehabilitation, and maintenance. Outputs are customizable and can be presented several ways. DARWin also has enhanced ESAL calculation procedures, report generation capabilities, display graphics, extensive on-line help, and many other features. DARWin 3.1 expands upon these features incorporated in previous releases of DARWin and provides many other enhancements in addition to being fully metric and English units compliant.

DARWin 3.1 is designed to run under Microsoft Windows^® 95, Windows^® 98, and Windows^® NT. DARWin accepts and calculates using both English and metric units, allowing the designer to convert from one unit system to the other "on-the-fly." DARWin 3.1, is a full 32-bit application which takes advantage of the multi-tasking environment of Windows^® and provides excellent screen graphics, which is a significant enhancement over previous releases of DARWin.

The DARWin software program is intended to serve as a design tool for the practicing pavement design engineer. A thorough understanding of the engineering fundamentals and principles associated with pavement design is essential to the proper application of this program. Although the modules in DARWin are simple enough to be operated by almost anyone from the engineering student to a design engineer, caution must be used since it cannot and should not take the place of the professional judgment of an experienced pavement design engineer. Many of the inputs to the design procedure are themselves a product of other design processes and must be thoroughly understood for sound pavement design. A user's guide with descriptions of the various software features and extensive examples help explain the capabilities of DARWin 3.1. While the software has extensive on-line help facilities, the first-time user of DARWin is strongly encouraged to use and reference both DARWin user’s guides and the appropriate edition of the pavement design guide extensively until they become thoroughly familiar with this product.

DARWin releases prior to July 1999 are equipped with a hardware security device, called Hardlock, to prevent unlicensed users from running unauthorized copies of DARWin. The Hardlock must be installed for DARWin to run.

DARWin releases after July 1999, will be equipped with a software security device that replaces the Hardlock. The software lock eliminates the need for and inconvenience of using the hardlock. Current users (as of July 1999) of DARWin 3.1 who would like to replace their hardware lock with the software lock can do so by returning their hardware lock along with a programming/processing fee as described in the “Current Fees and Licensing Options” section. Current network license users (as of July 1999) of DARWin 3.1 who would like to purchase additional network licenses of DARWin 3.1 will have their existing system upgraded to a software lock for the total number of licenses (existing licenses + new licenses).

DARWin releases earlier than DARWin 3.1 are no longer available for licensing through AASHTO.