Does cable median barrier work?
View video of cable barrier test
WSDOT engineers analyzed 11,457 median barrier collisions on Washington State highways from 1999 through 2004.
Percentage of median crashes that resulted in injury or death
- Cable barrier - 16%
- Concrete barrier - 41%
- W-beam guardrail - 41%
This is partly because cable barrier is far less likely to redirect an errant vehicle into a second vehicle in the collision. When additional vehicles are involved in a secondary collision, the risk of injury increases significantly.
Percentage of disabling and fatal crashes, the least frequent but most serious type of crash.
- Concrete barrier - 2.1%
- Cable barrier - 2.6%
- W-beam guardrail - 4.4%
Statewide, cable barrier successfully restrained 95 percent of errant vehicles without involving a second vehicle. In comparison, W-beam guardrail and concrete barrier successfully restrained 67 to 75 percent of crashes without involving a second vehicle.
What speeds are used for crash tests?
The highest speed used for testing is 100 kilometers per hour (approximately 62 mph). The federal government, other states and WSDOT have not conducted tests at higher speeds because less than 2 percent of all crashes exceed the speed and impact angle used in tests.
An increase in the test speed or change in vehicle type would affect the performance of all barriers WSDOT installs. Beam guardrail, precast concrete, rigid concrete and cable barrier systems are likely to exhibit periodic failures with increases in crash speeds or impact angles that are at the outer edges of the actual circumstances in which the barriers are anticipated to perform.
Keeping vehicles on the road
Over the last 10 years, WSDOT's efforts to improve highway safety have included engineering to help drivers keep their cars on the road and to lessen the safety consequences when they fail to do so. We have installed rumble strips, improved and straightened curves, widened highway shoulders, improved medians and installed median barriers.
While no barrier can eliminate the consequences for every driver who runs off the road, cable median barrier is expected to reduce the number of vehicles that cross a median and enter oncoming traffic. Cable median barrier is also an object that an errant vehicle may hit, as a result, the barrier is designed to minimize the forces on occupants in vehicles that hit the barrier and provide some capacity to redirect the vehicle in a controlled manner or bring the vehicle to a controlled stop.
What can drivers do? Because barriers can't protect every driver in every situation, drivers should take steps to avoid collisions:
- drive defensively
- adjust your driving for weather and traffic conditions
- allow adequate following distance
- never drive tired or under the influence of drugs or alcohol
- make sure that your vehicle's safety equipment is well maintained