Chapter 2 - Design Policies and Standards

2.2. Exceptions to Design Standards and Policies

2.2.1. Design Exceptions

If design features of a new construction or reconstruction project do not meet controlling criteria in the current edition of the AASHTO Green Book and the AASHTO publication, A Policy on Design Standards - Interstate System, as adopted by the Federal Highway Administration (FHWA), approval to build or retain the feature is required. For interstate projects, the FHWA is the agency which grants design exceptions. For all other projects, both Federal and State funded, the Chief Engineer grants design exceptions.  Guidance specific to non-interstate roadway resurfacing, restoration, or rehabilitation (3R) projects is provided in this Manual in Chapter 11, Other Project Types.

The following controlling criteria shall meet the requirements of the aforementioned AASHTO publications:

• horizontal alignment
• vertical alignment
• lane width
• shoulder width
• vertical grades
• cross slopes
• stopping sight distance
• super-elevation rates
• horizontal clearance (does not include clear zone)
• speed design
• vertical clearance
• bridge width
• bridge structural capacity

To obtain a design exception, a formal request shall be submitted using the format and procedures outlined in the GDOT Plan Development Process (PDP), Chapter 8.