The intersection of Iowa 330 and US 65 and Iowa 117 in Jasper County is one of the deadliest intersections in all of Iowa. Between 2004 and 2013, 101 crashes with 7 fatalities occurred along this 1 mile stretch of rural country road. Two more fatalities occurred in March 2015.
In 2011, the speed limit in this area was reduced from 65 mph to 60 mph.
Graphic courtesy of Iowa DOT website
Why not install traffic signals?
According to guidelines dictated by the Federal Manual on Uniform Traffic Control Devices, this intersection does not meet even one of eight warrants to consider installation of traffic signals in this area. However, alternatives were recommended by Neal Hawkins, CTRE Director, in his letter of December 16, 2014 to Scott Dockstader, Engineer for the DOT, after a study was conducted.
Instead of traffic signals, which the public would assume would be the most effective solution, the report states, “Traffic signal control along the expressway does not have the same crash reduction potential as the above two alternatives.”
What were those alternatives?
• Interchange – An interchange effectively eliminates the severe crash issues along the expressway. [Note: an interchange is a road junction that typically uses grade separation, and one or more ramps, to permit traffic on at least one highway to pass through the junction without directly crossing any other traffic stream.]
• J-Turn - The J-Turn positively addresses the crash issues faced by providing channelization in the median (physically prevents all drivers on the minor road from either crossing or making the left turn onto the major road).
Crossing and left turn maneuvers represent a minority of the possible vehicle conflicts at an at-grade expressway intersections but are involved in a majority of the severe right angle crashes. The J-Turn concept prevents these high risk maneuvers and substitutes these with low risk right turn and U-turn maneuvers.
Ultimately, the DOT has chosen a diamond interchange as the safest option, with construction slated to begin in spring 2017. Meanwhile…..slow down.