A good crowd of interested residents turned out for a public meeting held by the Missouri Department of Transportation Aug. 21 at the Osage Centre in Cape Girardeau to discuss the replacement of I-55 bridges over Highway 61 between Cape Girardeau and Jackson, and the conversion of the existing interchange to a diverging diamond interchange (DDI).
The $10 million project will replace the 578-foot long bridge spans with much shorter 200-foot spans. The bridges are in need of repair or replacement. According to Project Manager Jason Williams, the southbound bridge is in “poor” condition while the northbound bridge is in “fair” condition.
Highway 61, which currently passes under the interstate with a wide grassy median, will be redesigned into a DDI with concrete barriers separating the east/west lanes. Removing the grassy median will allow the highway to pass under the shorter bridge spans (which will still have room for a walking/biking trail).
In a DDI, the traffic lanes switch sides at traffic signals. Eastbound traffic from Jackson to Cape will switch from the south side to the north, and westbound traffic from Cape to Jackson will switch from the north side of the roadway to the south. After passing under the I-55 bridges, the lanes of Highway 61 will switch back to their normal sides of the roadway at traffic signals.
This switch allows for left hand turns to be made without crossing oncoming traffic, making the interchange safer.
A 2016 evaluation of diverging diamond interchanges across four states — Missouri, Kentucky, New York and Tennessee — found that road users could anticipate substantial reductions in crashes following the conversion of a conventional diamond interchange to a DDI.
There was a 67 percent reduction in right-angle crashes, a 41 percent decrease in injury crashes, a 36 percent decrease in rear-end crashes and a 33 percent decrease in total crashes.
Cape Girardeau has requested an additional traffic signal be installed at Veterans Memorial Drive. That signal, the two at the bridge, and the signal at Old Orchard Road on the Jackson side will be coordinated so drivers on Highway 61, if they have to stop at one light, will have green lights the rest of the way through the interchange.
Traditional signalized intersections have eight phases (so all left turns have turn signals). The traffic signals at the DDI will operate with only two phases, so wait times and traffic congestion at the intersections will be reduced.
Access to Wedekind Road on the south side of Highway 61 in Jackson will be permanently closed. Drivers will be able to access Wedekind Road by turning south at the Old Orchard Road signal.
A break in access will be included on Highway 61 so that a future road can be built between Old Orchard Road and I-55 on the south side of Highway 61. It will be further west than the current Wedekind Road intersection, because the current intersection is too close to the DDI.
“DDIs work well in heavily trafficked areas. The Center Junction interchange currently carries around 23,000 vehicles per day, which makes a DDI a great solution to meet the area’s growing demands,” said Williams.
Construction is expected to begin in summer 2019, with the completion anticipated in spring 2021. During construction, the Interstate 55 bridges will be replaced one at a time to allow one lane of interstate traffic to flow in each direction. Route 61 is not expected to close, but work will frequently require traffic to be reduced to one lane in each direction.
“We understand construction will involve some short-term inconvenience for motorists, but in the long-term this project will provide needed improvements in both safety and congestion,” added Williams.
For more information, please contact Williams at 573-472-5290, Area Engineer Brian Okenfuss at 573-472-9046, Transportation Project Designer Jeff Wachter at 573-472-5295 or MoDOT’s Customer Service Center toll-free at 1-888-ASK MODOT (275-6636).