Drivers who treat the Foristell exit like a second home are in for a big change. MoDOT is ripping out the old Interstate 70 interchange at Route T and Route W and rebuilding it as a "Divergabout," a mash-up of a diverging diamond interchange and a roundabout that is designed to keep traffic moving without signals. The overhaul is part of the statewide Improve I-70: Warrenton to Wentzville program, which will add a third lane in each direction and update a string of aging bridges. Crews are already in phased construction, laying temporary pavement, shifting lanes and routing traffic onto service-road detours, so local drivers and truckers should expect changing access near businesses through the summer work season.
What Is A Divergabout?
MoDOT’s public meeting handout, available from MoDOT, labels the new setup a "Divergabout" and calls it a combination of a diverging diamond interchange, also known as a DDI, and a roundabout. The design was picked to squeeze modern traffic flow into a relatively tight footprint, instead of sprawling out a traditional cloverleaf. The agency also points out that the roundabouts are being built big enough to handle semi-trucks that serve nearby businesses, so local freight traffic is not left playing bumper cars on tight corners.
For a deeper dive into the layout and construction phasing, see reporting from the St. Louis Post-Dispatch.
What Drivers Should Expect
MoDOT has announced that the eastbound I-70 on- and off-ramps at Route T/W will be closed overnight on June 30 and July 1 for paving, with signed detours in place for affected traffic, according to MoDOT. Project materials and the construction schedule outline other summer disruptions, including 45- to 60-day partial closures of service roads, stretches of temporary pavement to keep movements open and a 23-hour eastbound bridge demolition window. Regular commuters should plan on extra drive time and follow the posted detours as crews build the new ramp terminals and roundabouts.
Timeline And Local Impacts
St. Charles County planning documents show that the rebuild includes a 10-foot multi-use path on the east side of the new interchange to improve bicycle and pedestrian connections, and that this pedestrian access piece is already under construction with completion expected in 2026, according to St. Charles County. The Divergabout is one piece of the broader Improve I-70 project that aims to modernize the corridor and reshape how local roads plug into the interstate, affecting everything from neighborhood cut-through routes to how trucks reach industrial sites.
How To Stay Updated
Residents who want real-time construction notices and phasing videos can watch the Foristell project live feed and sign up for local alerts through the City of Foristell's website, which links to project materials and Improve I-70 contacts. For specific questions about property access, business entrances or safety in the work zone, the county transportation planning office and MoDOT list phone numbers and email addresses in their public documents, so frustrated drivers have someone official to call instead of just yelling at the orange barrels.
