Cable Barrier

Median cable barriers

Cable barrier stops a vehicle in the median
See photos of collisions involving cable median barrier (Flickr).

We install cable guardrail because it helps keep motorists safe. Severe injuries and fatalities often result when a vehicle crosses the median and collides with oncoming traffic. We install barriers in highway medians to help reduce injuries and fatalities.

Choosing the right barrier for the job

Before installing barriers in medians, our engineers carefully consider whether barriers would enhance safety, and if so, which type of barrier would work best for each location. They consider a wide array of factors:

  • collision trends and history
  • traffic speeds and volumes
  • road grade, angle and curve
    available median and shoulder space
  • slope of the median
  • barrier characteristics
  • installation and maintenance costs

We use three general types of highway barrier: cable barrier, beam guardrail and concrete barrier. All of these barriers are designed to reduce injury severity through containment and redirection. All of the barriers we use today have been evaluated and have passed uniform federal crash test criteria.
 
WSDOT's policy for the use of cable barrier systems has evolved as more information and new technology becomes available. One such advancement that WSDOT has adopted for new installations is the use of a 4-rope barrier system versus a 3-rope system. The 4-rope system has a lower bottom cable and a high top cable which helps decrease the potential for vehicles to get under or over the cables. As a July 2011, there have not been any cross median crashes involving 4-rope systems. In addition, 85% of the crashes into the 4-rope systems have been non-injury.

Safety benefits of cable median barrier
 

Our goal is to reduce collisions involving vehicles crossing the median and colliding with oncoming traffic. Cable barrier has been shown to significantly reduce the number of fatal and serious injury collisions. According to statewide statistics, 95 percent of cars that hit the cable barrier are stopped from crossing the median.

No barrier is 100% effective in reducing injuries and containing errant vehicles, but cable barrier greatly improves safety for drivers. The American Association of State Highway and Transportation Officials’ (AASHTO) benefit/cost analysis of cable median barrier showed such projects to be among the highest benefit safety investments to prevent fatal and serious injury collisions.
 

Median cable barrier retrofit

In 2009, WSDOT received $9 million in funding from the American Recovery and Reinvestment Act (ARRA) to retrofit low-tension cable barrier at various locations around the state. These funds supported projects that realigned and replaced low-tension cable barrier with high tension cable barriers. Work was completed in November 2010.
 

The history of cable barrier

New York was the first to develop a 3-rope cable barrier system resembling modern day cable barrier. This system originated as a roadside barrier and later found use as a median barrier. Cable barriers have continued to evolve from that beginning and are now used by nearly all of the states.