COLUMBIA ― A study by MU researchers shows that J-turn intersections have decreased vehicular accidents and deaths in Missouri.
J-turns are relatively new to Missouri; the first in Columbia opened in 2012. These intersections are supposed to make crossing to the far side of divided highways safer.
And in a new study funded by the Missouri Department of Transportation that was released Monday, Praveen Edara, Carlos Sun and Sawyer Breslow of MU's College of Engineering found that these intersections have done just that.
According to the report, injury accidents at intersections with J-turns have decreased by 53.7 percent, while overall crashes have decreased 34.8 percents. T-bone crashes, which are particularly dangerous, were eliminated altogether at the intersections studied.
"This study is just validation that J-turns are an effective solution for intersection design," said John Miller, a traffic safety engineer with MoDOT.
Using a J-turn involves a few steps. Instead of waiting for traffic on both sides to clear up, drivers turn right onto an acceleration lane, merge into traffic and then drive through the passing lane onto a deceleration lane on the left.
Once in the deceleration lane, drivers make a simple U-turn onto another acceleration lane before merging right into the passing lane on the other side of the highway.
Although J-turns are a triumph for traffic engineers, they are not popular with everyone. Complaints include difficulty merging after the U-turn, improper use of the acceleration and deceleration lanes, and general confusion, the report stated.
At Meek's Lumber and Hardware off U.S. 63 in south Columbia, most employees encounter a J-turn on their way home, said Hollie Holmes, the store's bookkeeper. Most people are familiar with the intersection now, Holmes said, but it has made it difficult to get shipments in and out.
The J-turn can be difficult to navigate during rush hour, Holmes said, and it can be especially disorienting for people from out of town.
But J-turns don't appear to be going anywhere soon. The first J-turn appeared in Missouri in 2007. When the MU researchers began their study, there were only five in the state. There are now 13, Miller said.
And the intersections are far cheaper than alternatives. Constructing a new interchange to get across divided highways can cost about $10 million, whereas a J-turn costs only about $1 million.