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Section 9: Emergency Crossovers

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Overview

Emergency crossovers may be provided when needed to facilitate emergency and law enforcement vehicles. Coordination with local and state law enforcement and emergency services personnel is recommended to identify roadway sections where crossovers may be necessary.

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Location

When selecting a location for a crossover, the following guidance should be used:

  • Do not install emergency crossovers in urban locations. Interchanges are closely spaced and provide opportunities for making needed turn movements.
  • Emergency crossovers should be spaced at approximately 2 mile intervals, except where coordination with local and state law enforcement has identified a need for spacing of crossovers of less than 2 mi. [3.2 km] to address local issues.
  • Emergency crossovers should be placed at reasonable intervals based on engineering judgment and safety, generally no closer than ½ mi. [0.8 km] between crossovers.
  • The emergency crossover is not to be located within 1500 ft. [457.2 m] from any ramp terminal or other access connection.
  • The emergency crossover is not to be located within curves requiring superelevation, unless field engineering determines the location is safe and reasonable for emergency use.
  • Emergency crossovers should be located where more than minimum stopping sight distance is provided.
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Construction

When ending a run of cable barrier, the cable barrier terminals should be located, when possible, behind some protection such as the MBGF, leaving adequate distance to allow an emergency vehicle to maneuver around if necessary. See Figure A-15.

Cable Terminals Behind Metal Beam Guard Fence (click in image to see full-size image)

Figure A-15. Cable Terminals Behind Metal Beam Guard Fence

The terminals can be placed in locations with no protection, but since they provide the anchorage for the cable barrier system, protecting them from possible hits is recommended. These terminals are also gating (meaning they will not prevent a vehicle from going through).

When switching the cable barrier from one median side to the other and the terminals are not protected, overlapping the runs of cable barrier is recommended to provide adequate protection from possible crossovers if the median is wide enough to allow emergency vehicles to utilize it as an effective emergency crossover. (See Figures A-16 through A-17).

Recommended Cable Barrier Lap Length (click in image to see full-size image)

Figure A-16. Recommended Cable Barrier Lap Length

Another typical layout for emergency crossovers may be as shown below.

Another Typical Layout for Emergency Crossovers (click in image to see full-size image)

Figure A-17. Another Typical Layout for Emergency Crossovers

  • Emergency crossovers should be an all-weather surface. It is recommended that they be constructed with a surface treatment that does not invite use. Grade 1 or 2 aggregate or bladed recycled asphalt pavement (RAP) has provided an adequate low cost surface in some applications.
  • Emergency crossovers should be approximately 20 ft. [6.1 m] with return radii of 10 ft. [3.0 m]. Wider crossovers invite non-emergency use and should only be constructed after an engineering study of the site.
  • To be inconspicuous to main lane traffic, the surface should be depressed below the shoulder level, if possible.
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