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Strategy C2. Redesign Intersection ApproachesNCHRP Report 500 / Volume 12: A Guide for Reducing Collisions at Signalized Intersections WHERE TO USESignalized intersections with safety problems related to sight distance that cannot be addressed with less expensive methods.
DETAILSIf other less expensive methods cannot be used or are ineffective, horizontal or vertical (or both) realignment of approaches may be a solution. Realigning both of the minor road approaches so that they intersect the major road at a different location, or a different angle, can help address horizontal sight distance issues. This is a high-cost, longer-term treatment for the intersection, but if completed according to applicable design policy, it should help alleviate crashes related to sight distance. The AASHTO Policy on Geometric Design of Highways and Streets contains sight distance guidelines, and these guidelines should be considered when revising intersection approach geometry. An intersection leg can be closed or can be made one-way away from the intersection in order to address sight distance issues related to that particular leg. Intersection relocation and closure, elimination of intersection skew, and offsetting of left-turn lanes are all strategies that involve improvements to approach alignment to improve sight distance. KEY TO SUCCESSThere are significant right-of-way and property access issues involved in this strategy, and public information campaigns are vital to the success of the intersection improvements. ISSUESOwners of properties where access would be reduced, especially owners of commercial operations, may oppose this strategy. Thus, careful evaluation of the potential impacts of proposed improvements is needed to avoid or minimize such problems. TIME FRAME: LongThis strategy requires a long implementation time. At least one year is necessary to work out the details of intersection approach realignment and to communicate the plan to affected businesses owners and residents. Where relocation requires right-of-way acquisition and/or demolition of existing structures, an extensive project development process of up to four years may be required. COSTS: HighThe costs to change the horizontal or vertical alignment of an intersection approach are usually high. Furthermore, additional right-of-way will generally need to be acquired. EFFECTIVENESSPROVEN: Implementing any of these strategies should improve safety at signalized intersections. More research is needed to better quantify estimates of crash reduction for these countermeasures. COMPATIBILITYThis strategy can be used in conjunction with other strategies for improving safety at signalized intersections. For more details on this and other countermeasures: http://safety.transportation.org For more information contact: FHWA Office of Safety Design FHWA Resource Center – Safety and Design Team 
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Program ContactEd Rice Jeffrey Shaw What’s NewRoundabout Outreach and Education Toolbox Stop-Controlled Intersection Safety: Through Route Activated Warning Systems Roundabouts: An Informational Guide, Second Edition (NCHRP Report 672) Roundabouts Peer-to-Peer Assistance How to drive a roundabout (WSDOT) Modern Roundabouts: A Safer Choice FHWA's Intersection Resources Library CD-ROM HighlightsMini-Roundabouts Technical Summary Access Management in the Vicinity of Intersections Technical Summary Intersection Safety Case Studies Intersection Safety Technologies Presentation: Intersection Safety Example Intersection Safety Implementation Plan |
