Cable spot up to soil, road slope

While traveling Arkansas interstates, I’ve noticed retaining fences are close to one lane, but a few miles down the road they’re close to the opposite lane. They seem to change at an overpass or small bridge over a low area. Why is that? Wouldn’t it be safer if they put the retaining fences in the middle of the median?

— Just Wondering

Dear Wonder: These things are more properly called cable median barriers. They are designed to keep errant vehicles on their own side of an interstate, rather than have the vehicle cross the median into oncoming traffic. The latter is particularly unsafe, especially at interstate speeds.

(Whoa. That sounds … knowledgeable. Nah. We have written about cable median barriers for years and have done some additional “research.”)

Why do the barriers vary in their positioning?

One factor is the slope, Arkansas Department of Transportation spokesman David Nilles said.

It would be a bad thing for an out-of-control vehicle to vault over the cable into opposing traffic, so the barrier is placed where it has the best chance of catching that vehicle. The middle of the median might not be that best place. Oftentimes the middle is the lowest point, so the cable is placed on one side or the other depending on which side is highest and more likely to catch the vehicle.

In addition, the soil in the lowest point of a median can also stay too wet to provide the solid foundation the posts need. So if one direction of the interstate is higher than the other, that side of the median usually gets the cable.

Engineers also review which side of the road has had more drivers heading into the median, Nilles said. They’ll place the cable on the opposite side to give the veering drivers more room to recover on their own.

Dear Mahatma: Cable median barriers may work for cars, but they are deadly for motorcyclists.

— Just Bob.

Dear Bob: You refer to a highway fatality earlier this year in which a motorcyclist on Arkansas 64 in Faulkner County left the roadway and struck a cable median barrier.

There is some research on this matter of barriers versus motorcycles. The research comes from all over the world.

One study we attempted to read analyzed nearly 1,000 motorcycle accidents in North Carolina, Texas and New Jersey. The authors concluded that no definitive evidence shows that cable median barriers are more dangerous to motorcyclists than concrete barriers or guardrail barriers. The authors acknowledged the issue is “greatly debated.”

Australian researchers concluded guardrail barriers were more dangerous to motorcyclists than wirerope barriers. The study also said that when a motorcyclist strikes an object “that is solid relative to the human body,” survivability rapidly reduces at body impact speeds over 40 kilometers per hour — 25 mph.

Vanity plate seen on a Corvette: CATCHME