Kris from Stillwater noticed something curious about the cable barriers strung along the medians on many of our highways and freeways.
Sometimes they are in the middle of the median, and other times they are right up against the traffic lanes and jump from one side of the highway to the other.
Why the difference?
Cable barriers — made of three or four steel cables strung on posts — are designed to keep out-of-control vehicles from crossing the highway and crashing into oncoming traffic.
They work like this: When a car hits the barrier, the posts break and the cables flex, absorbing much of a crash's kinetic energy. This redirects the vehicle along the median, preventing a cross-median crash. Minnesota Department of Transportation (MnDOT) officials say the barriers can reduce fatal crashes by 90 percent.
They first appeared on Interstate 94 between Rogers and Maple Grove in 2004. Since then, they have been installed on hundreds of miles of grassy medians in highly traveled areas where such crashes have or could potentially occur. More recently, the barriers were installed along Interstate 94 through Woodbury.
While many barriers run right down the middle of the median, that isn't always the best place.
The middle is often a low spot, so there's a "distinct possibility" of an errant vehicle vaulting over the cables. The soils are often poor, said Kent Barnard of MnDOT.