128.9 Documentation of Design Exceptions

Documentation of design exceptions is necessary for the department to be able to defend itself from litigation. Litigation may take place many years after the actual construction and permanent documentation is necessary to determine the justification for design exceptions.

Design exceptions consist of items that vary from published MoDOT design criteria. In most cases the need for design exceptions are the result of the inability to reasonably meet the preferred design criteria specified in this document. However, there are occasions where the improvements will greatly exceed the normal criteria recommended for the type of improvement. These variations must also be documented through the design exception process. When there is doubt if a design exception is required, the design liaison engineer should be consulted.

The preferred design criteria for new construction on rural and urban highways, 3R and 4R projects are available in various EPG locations:

230.1 Horizontal Alignment,

230.2 Vertical Alignment,

231 Typical Section Elements for Roadways,

232 Facility Selection,

233 At-Grade Intersections,

234 Interchanges,

236.13 Designing for Right of Way, and

748 Hydraulics and Drainage.

The criteria for proper access management can be found in MoDOT’s Access Management Guidelines. On urban projects, turning lane width and whether the pavement is curbed or uncurbed are noted on this form. A Design Exception Information form is not required if all established design criteria are used.