Vertical Displacement
Raised Intersections

A raised intersection slows drivers, in that drivers must slow to avoid physical discomfort.

A raised intersection is a raised plateau, usually 3 to 6 inches above adjacent streets (Dixon et al. 2008). A raised intersection slows drivers in a manner similar to a speed table, given drivers must slow to avoid physical discomfort.

Advantages

  • Can slow vehicles in critical problem areas (City of Palos Verdes Estates 2001)
  • Provides visual clues to drivers
  • Proven safety countermeasure

Disadvantages

  • Requires additional maintenance
  • May have an impact on drainage
  • May have an impact on turning movements (City of Palos Verdes Estates 2001)
  • Need to warn drivers about them

Effectiveness

Ewing (1999) indicated minimal speed reductions, given vehicles may already be slowing for the intersection. In other cases, raised intersections may have the same effectiveness as speed tables.

The Crash Modification Factors Clearinghouse provides a crash modification facor (CMF) of 1.05 for injury crashes for raised intersections.

Appropriateness

Raised intersections can be applied to rural main streets, particularly those with high pedestrian volumes. Raised intersections affect traffic operations, so large trucks and farm equipment should be considered.

Cost

Installation of raised intersections is a major investment.

References

City of Palos Verdes Estates. Traffic Calming Program. City of Palos Verdes Estates, California, 2001.

Dixon, Karen, Hong Zhu, Jennifer Ogle, Johnell Brooks, Candice Hein, Priyank Aklluir, and Mathew Crisler. Determining Effective Roadway Design Treatments for Transitioning from Rural Areas to Urban Areas on State Highways. Report FHWA-OR-RD-09-02, Final Report SPR 631. FHWA, Oregon Department of Transportation, 2008.

Ewing, Reid. Traffic Calming: State of the Practice. Washington, DC: Institute of Transportation Engineers, U.S. Department of Transportation, 1999.

Hughes Warren, Debra Chappell, and Shyuan-Ren (Clayton) Chen. Chapter 6. Geometric Design Treatments. Innovative Intersection Safety Improvement Strategies and Management Practices: A Domestic Scan. Federal Highway Administration, 2006.

SCDOT. SCDOT Traffic Calming Guidelines. South Carolina Department of Transportation, Traffic Engineering, Columbia, SC, Revised 2006.

Raised intersection (Hughes et al. 2006)

Drawing: Cross-section schematic for a typical raised intersection

Cross-section of a typical raised intersection (SCDOT 2006)


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