scope:

SCOPE OF GUIDELINES

The guidelines presented in this document are intended for application in the design of very low-volume local roads, as defined above, including application in both new construction and in the improvement of existing roads. The scope of the guidelines includes roads in both rural and urban areas.

The design guidelines enable designers for projects on very low-volume local roads to apply design criteria that are less restrictive than those generally used on higher volume roads. The risk assessment on which the guidelines are based shows that these less restrictive design criteria can be applied on very low-volume local roads without compromising safety. The guidelines discourage widening of lanes and shoulders, changes in horizontal and vertical alignment, and roadside improvements except in situations where such improvements are likely to provide substantial safety benefits. Thus, projects designed in accordance with these guidelines are less likely to negatively impact the environment, roadway and roadside aesthetics, existing development, historic and archeological sites, and endangered species. In reviewing the geometric design for sections of existing roadway, designers should strive for consistency of design between that particular section and its adjoining roadway sections. The potential effects of future development that may affect the traffic volume and vehicle mix on the roadway should also be considered.

The design guidelines are intended to encourage rational safety management practices on very low-volume local roads. Expenditures for safety improvements are discouraged at sites where such improvements are likely to provide little safety benefit, but are strongly encouraged at sites where safety problems exist that can be corrected by a roadway or roadside improvement. Designers are provided substantial flexibility to retain the existing roadway and roadside design, where that existing design is performing well, but are also provided flexibility to recommend improved designs, even designs that exceed the guidelines presented here, where necessary to correct documented safety problems.

The scope of the guidelines includes geometric design for new construction and for improvement of existing roads. Geometric design criteria for new construction apply to construction of a new road where none existed before. Projects on existing roads may involve reconstruction, resurfacing, rehabilitation, restoration, and other types of improvements.