Tag Archives: cable barrier

How effective is freeway median cable barrier?

The in basket: John Rosinke of Silverdale wrote me on July 10 to say, “Read your column today and proceeded down the page to the Code 911 section. Noticed a pickup truck was able to cross the cable barriers on Route 16. Seems like I read several other reports that vehicles do cross cable barriers. Aren’t they supposed to prevent crossing to the oncoming lanes?”

The accident in question led to the death of the man whose pickup truck crossed the barrier.

I can recall reading of only one other such accident, also a fatality, but I’m sure there have been others.

I asked the state about the reliability of cable barrier in keeping out-of-control vehicles from crossing the median into the oncoming lanes.
The out basket: Claudia Bingham Baker of the state highway department said, “Yes, we do look at the conditions surrounding collisions in which vehicles breach cable barrier. We promptly repair the cable barrier when hit, and we also do annual inspections of the cable barrier to ensure it is in good working order and at the proper tension.

“A little background on cable barrier might be helpful. Cable barrier, like all barrier, is not designed to prevent all collisions. It is designed and built to certain criteria. When vehicles exceed those criteria with speed, momentum, angle of impact or other factors, cable breaches can and do occur.


“(This state) has been using cable barrier in various locations since about 1995. Over a three-year period in the mid-2000s we did formal performance reviews of the efficacy of cable barrier and found that they are a worthwhile and cost-effective method to deter traffic from crossing medians and into opposing lanes.


“For example, in 2007 we found that 95.1 percent of vehicles that hit cable barrier did not cross into opposing traffic lanes. (Also) cable barrier is designed to flex upon impact, which dramatically reduces the impact forces on errant vehicle occupants when compared to solid types of barrier.


“We also can treat more miles per dollar with cable barrier, and that difference can be significant. Depending on site conditions and other factors, we can treat 1.5 to 6.3 times the mileage with cable barrier than with other barrier, such as concrete.


New median cable barrier adds a strand

The in basket: I was surprised to read in Monday’s Sun that  cable barrier projects would be beginning this week on Highway 16 from Purdy to Sedgwick Road.

I was surprised because I’d seen cable barrier being replaced at the Burnham Drive interchange in Gig Harbor on Feb. 11. It seemed like the work had started much earlier.

The new metal uprights at Burnham Drive looked taller to me. and the cables farther from the ground

The motorcycle community is no fan of the cable barriers. Some call them cheese cutters, more from anticipation of what it would be like to slide into one than from actual experience with such a mishap, I think.

Not expecting to be right, I asked if the new barrier would allow a motorcyclist to slide under the bottom cable.

The out basket: And I wasn’t right. It’s got nothing to do with motorcycles specifically.

And it’s a separate project from the one described in Monday’s paper. Though Peterson Brothers of Sumner has both jobs, Dennis Engel’s project office in Tumwater is supervising the work just starting.

Andy Larson with the state’s Port Orchard Project Office supervised the Burnham Drive job that extends up the hill to the Highway 302 exit.

“The safety improvement project replaces and extends the current three-strand cable barrier with a high-tension four-strand system,” he said. “The additional strand is probably what made the barrier seem higher than the existing one.

“Once the four-strand cable barrier (was) in, the three-strand cable rail (was) removed,” Andy said. “In this project we have also installed new guardrail along the outside of SR 16.”

Dennis Engel explained the genesis of the work, called the Olympic Region Redirection Landform Mitigation project.

“Over the years, we have built up berms under the bridges, and the landforms aren’t as effective as they could be. So we add cable barrier and guardrails to protect people.”

Though a lot of three-strand cable barrier was replaced at Burnham Drive, Dennis said not much would be at the three interchanges his office is supervising.

The Purdy part of the project is at the northern interchange, on the on-ramp from Purdy to go north toward Port Orchard.

I wondered if perhaps the three-strand barrier had been discredited by accident figures, but couldn’t get a clear idea on that.

The Federal Highway Administration does says on an online site that “Research by the National Crash Analysis Center found that adding a fourth cable to the generic three-cable design increases the likelihood that the cable barrier will catch a broader spectrum of vehicles.

“Tensioning the cables after installation improves the performance of the system by reducing deflection and increasing the potential to capture the impacting vehicle,” it said.