What is a J-Turn?
The "j-turn" is an alternative to traditional roadway intersections on a four-lane highway. Instead of motorists crossing fast-moving lanes of traffic to get to the opposing lanes, drivers at a j-turn intersection turn right in the same direction of traffic, merge into the left lane, and then make a left turn in the direction they intend to travel.
In addition, acceleration lanes are constructed to allow traffic an opportunity to gain speed after turning onto the highway.
Although drivers will have to travel slightly further to get where they want to go, using J-turns can take the same or less time than trying to wait for a safe and appropriate gap to cross traffic.
Why are J-Turns Safer?
The point of these turns is to greatly reduce – or even eliminate -- a significant number of severe crashes common when drivers must cross-over busy highways to reach another road.
In a traditional intersection there are 42 different conflict points when an accident can occur. Twenty-four of those 42 conflict points are accidents that are crossing conflict points and are severe in nature (i.e. T-bone and right-angle accidents). A J-Turn intersection can have no more than 29 possible conflict points. And J-Turn intersections can be designed so that there are zero crossing conflict points.
What are Conflict Points?
"Conflict points" are the points were two vehicle paths cross, which means the point where there is a potential for a crash.
Crossing conflicts (the pink dots below) tend to result in serious accidents.
Traditional Crossing Intersection Diagram
University of Missouri-Columbia Study Shows J-Turns Eliminate
Crashes & Cut Injury Crashes in Half
A recent study conducted by the University of Missouri shows that implementing the J-turn design at intersections of high-speed rural expressways and minor roads results in fewer accidents than those that are controlled by two-way stops.
Researchers assessed five different J-turn intersections in Missouri:
- The J-turn design resulted in a 34.8 percent reduction in crash frequency for all crashes
- A 53.7 percent reduction in crash frequency for all injury and fatal crashes.
- Disabling injury crashes decreased by 86 percent and minor injury crashes decreased by 50 percent.
- Since the J-turns have been in place, none of the five study sites had a single fatality accident.
- One of the most severe crash types, the left turn, right angle crash, was completely eliminated by the J-turn.
One location is the J-turn at Highway 63 and Deer Park Road just south of Columbia. Prior to the J-turn, there was an average of about 13 crashes annually for three consecutive years. Now with this new, innovative design, only six accidents occurred in the year after it was installed, half the number of accidents experienced prior to the J-turn.
LINK: FULL UNIVERSITY STUDY ON J-TURNS & ROUTE 63 J-TURN SURVEY RESULTS
MoDOT CENTRAL DISTRICT INFORMATION VIDEO ON J-TURNS
HOW DO YOU DRIVE A J-TURN?