9.6 Intersections

intersections at right angles

avoid complex intersections

separate intersections

use 't' intersections for tertiary streets

separate intersections

provide adequate site distances at intersections

Intersections are the most dangerous areas of the installation circulation system.  They should be planned or improved to provide safe and efficient traffic flow for both pedestrian and vehicular traffic.  The following design techniques should be used to plan or improve intersections:

• All roadways should intersect at right angles (90 degrees), although 85-95 degrees is acceptable. 

• Avoid dangerous, complex intersections of more than two streets intersecting at one point or offset intersections. 

• Eliminate intersections that are in close proximity to one another.  They should be no closer than a minimum distance of 30 meters (100 feet).  Consolidate opposing intersections into a four (4) way configuration whenever possible to reduce the number of traffic conflict points.

• Use T-intersections for tertiary road intersections with secondary or primary roads to reduce conflict and promote safety. 

• Provide turning lanes at all intersections along primary roads to eliminate interference with through-traffic flow. 

• Minimize intersections along primary roads to reduce points of conflict and increase safety. Existing intersections with secondary and tertiary streets can be eliminated by the use of cul-de-sacs with traffic routed along parallel streets to primary and secondary streets. 

• Include adequate sight distances to meet minimum standard requirements at all intersections.  The appropriate sight distance triangle will be determined based on intersection geometry, approach speeds, intersection traffic control and site conditions.  Sight angle distances will be determined using standard sight distance formulas from IAW A Policy on Geometric Design of Highways and Streets.

• Minimize pedestrian and bicycle intersections with primary streets.

• Provide crosswalks at all intersections where necessary.  The crosswalks shall be properly marked with paint or vinyl strips or identified with a different paving surface and shall have the proper signage.  Mid-block crosswalks may be utilized as necessary to support regular pedestrian crossing activities at locations other than road intersections.

• Provide pedestrian access to persons with disabilities in accordance with the Americans with Disabilities Act Accessibility Guidelines (ADAAG) and the Uniform Federal Accessibility Standards (UFAS).  In the event of a conflict, the most stringent standards will be applied.

• Create local service drives or access roads to parallel highways and primary roads to provide access to properties fronting the primary road avoiding a direct curb cut from the primary road to each individual property.

• Intersections between railroad tracks and primary  roads must be signaled, well marked, and have a smooth transition.  All other road crossings must be well marked and have clear line-of-sight down the tracks.

• Grade at intersections shall be no greater than 4%.

Circulation Design Standards