Chapter 5 - Roadside Safety and Horizontal Clearance

5.3. Urban Shoulder Horizontal Clearance

Horizontal clearance on urban roadways is not based entirely on the clear zone concept due to various pre-existing conditions and urban roadway shoulder constraints, although clear zone considerations may apply under certain conditions, such as run-off-road (ROR) crash history, excessive volumes, geometric conditions, excessive operating speeds, new location construction, etc. Urban roadways are generally confined on the roadside and are posted at speeds of 45 mph or less. According to the AASHTO Roadside Design Guide, the presence of curb and gutter within the roadside, even barrier-faced, does not generally redirect a vehicle, especially at speeds above 25 mph. Horizontal clearance for urban roadways is based on the specific feature or element being considered, and generally is related to a combination of environmental, operational and safety characteristics, both for pedestrians and vehicular traffic.

According to the AASHTO Roadside Design Guide, Chapter 10. Roadside Safety in Urban or Restricted Environments, uniform horizontal clearance between traffic and roadside features is desirable (2006). It is GDOT’s intent to facilitate this principle as much as practical, using this guide and ongoing education and collaboration with GDOT staff and participating stakeholders.

The GDOT Pedestrian & Streetscape Guide, written and maintained by the GDOT Office of Planning , has direct application on urban shoulder usage. The GDOT Pedestrian & Streetscape Guide provides guidance for design professionals, developers, municipalities and others regarding the design, construction, and maintenance of pedestrian facilities.

The GDOT Office of Utilities employs the GDOT Utility Accommodation Policy and Standards Manual to guide decisions for utility facility placement on public right of ways. Both rural and urban conditions are addressed in this document.

From an operational perspective, the horizontal offset of 1-ft., 6 in. from face of curb to fixed object stated in the AASHTO Green Book (2004) shall be an absolute minimum horizontal clearance for urban roadways. If this controlling AASHTO criterion is violated, a design exception will be required.