9.5 Roadway System Design

The location and design of new circulation system alignments, as well as improvements to the existing system, should be prepared to promote sustainability. They should be designed to minimize impacts, relieve driver monotony, and provide a positive visual experience for the user, without compromising safety. The following design techniques should be applied to circulation system design.

9.5.1 BLEND CIRCULATION WITH NATURAL LANDFORM

align along forest edge

monotonous alignment

interesting alignment

The horizontal and vertical alignment of roads, walkways, and bikeways should minimize landform disturbance and blend with the natural setting.

Minimize cut and fill by steeping terrain and aligning roadway, walkway, or bicycle system to cross slopes diagonally or parallel to the contours rather than perpendicular to the contours.

Mold cut and fill slopes to blend into the natural landform.

Blend road drainage ditches, swales, or channels into the natural landform.

Use cluster development wherever possible to limit the lengths and required intersections of roadway and other circulation system elements and to preserve land. Consideration should be given to meeting antiterrorism requirements when developing cluster-type facilities.

Minimize pedestrian, railroad, and bikeway crossings of highway, primary, and secondary roads.

Use natural topographic conditions to create grade-separated pedestrian, railroad, and bikeway road crossings wherever possible, especially on highways and primary roads.

9.5.2 ADAPT CIRCULATION TO PRESERVE VEGETATION

Design roads, walkways, and bike paths to minimize disturbance to existing vegetation, encourage re-vegetation in disturbed areas, and reduce the visual impact of landscape disturbance.

Align roads through open areas rather than forested areas.

Minimize cut and fill to reduce the limits of clearing.

Clear vegetation only for sight distances at intersections rather than uniform right-of-way clearing.

Utilize tree wells or retaining walls to preserve specimen trees or significant vegetation areas.

Provide optimum conditions for re-vegetation by following proper planting and maintenance techniques.

Restore vegetation to disturbed areas using naturalistic plantings of native plant material.

9.5.3 MINIMIZE ADVERSE IMPACTS ON ADJACENT LAND USES

utilize buffers

Locate roadway alignments to minimize the impact of air pollution from traffic-emitted pollutants on adjacent development. This can be accomplished by the following:

Locate roads adjacent to land uses that are minimally affected by traffic-emitted air pollutants.

Reduce the impact of traffic-emitted pollutants on more sensitive land use areas by locating the roadways downwind and/or providing planted buffers. Tactical vehicle trails should be hard-surfaced in populated areas to reduce dust pollution.

separate roads from facilities

Design and locate roadways to reduce the impact of traffic noise on adjacent development.

Roads should be physically separated from sensitive land uses including residential, medical, educational, recreational, administration, religious, library, community, or child care facilities.

Utilizing noise abatement techniques such as berms, sound barrier walls, and plant material to reduce noise levels.

Reroute truck and tank traffic to roadways adjacent to less noise sensitive land uses. Ideally, tracked vehicle traffic should be routed to a system of tank trails that are totally separate from corridors used by wheeled traffic vehicles.

9.5.4 fire lane requirements

Fire lanes shall be provided for all buildings that are setback more than 150ft from a public road or exceed 30ft in height and are setback over 50ft from a public way. In addition, if a building does not have 360 degree access, a fire lane shall be provided to the rear of the building. This fire lane may be a sidewalk with a minimum width of 20ft of drivable surface.

Fire lanes shall be not less than 20ft of unobstructed width, able to withstand live loads of fire apparatus and have a minimum of 13ft 6in of vertical clearance. An approved turnaround for fire apparatus shall be provided where an access road is a dead end and is in excess of 150ft in lenght. The turn around shall have a minimum centerline radius of 50ft. The grade of the fire lane shall be within the limits established by Fire Prevention.

See the Fire Department Standards in Appendix B for more information