They've been known to save lives along some of Kentucky's busiest highways.
But many parts of Interstate 75 that have seen many deadly crossover crashes still don't have protective barriers.
On Wednesday, three people were killed on I-75 in Laurel County after a station wagon crossed the median and hit a car head-on.
It happened on a stretch without a protective barrier.
Officials say those barriers can save lives or at least cut down on the number of crossover accidents.
The Kentucky Transportation Cabinet is addressing the issue.
I-75 in Fayette County has concrete barriers dividing the two directions of traffic. But if you head south of Lexington, many areas don't have them.
In Laurel County, for example, there are barriers between mile markers 33 and 41. But other stretches don't have them, although they're planned to be installed between mile markers 41 and 48 within the next six years.
Some officials say barriers can work against drivers. For example, a car that hits a barrier can actually be deflected back into traffic.
Cable barriers are another option. They were installed along parts of New Circle Road this year. But they can be more expensive.
Officials say there's no current plans to install barriers along every stretch of I-75 in the near future.
Transportation Cabinet officials say they examine how many crossover accidents a stretch of road has before seeing if barriers are necessary.