RIGBY - Northbound traffic on U.S. 20 in Thornton will be moved back to northbound lanes and to newly constructed northbound ramps of the Thornton Interchange Wednesday (May 25). The return to northbound lanes, between milepost 327 and 330, will allow two lanes of traffic in each direction during the upcoming Memorial Day holiday.

The new interchange will improve safety and operational effectiveness by eliminating the final at-grade (level) intersections with U.S. 20 in the 34 miles between Idaho Falls and Sugar City. The route will be a full-access control divided highway, improving safety, mobility and economic opportunity for the public.

It also will connect Madison County’s planned 5000 South project, designed to improve traffic flow in the southern part of the county.

The project is scheduled for completion in October.

The speed limit will be 55 mph, and commercial vehicles will be restricted to 14 feet in width. Motorists should obey all traffic signs and watch for construction workers and equipment Monday through Saturday when work is under way.

Starting Thursday, June 2, southbound traffic will be diverted onto the northbound passing lane so that crews can construct southbound ramps of the new interchange. Both northbound and southbound traffic will detour around the east side of the new interchange on the newly constructed northbound ramps.

The interchange (overpass) project will elevate U.S. 20 to pass over 4700 South and will realign this county road north of its current location.

Commercial drivers transporting permitted loads wider than 14 feet need to contact Resident Engineer Wade Allen (208-745-5680) or Staff Engineer Bryan Young (208-745-5682) 24 hours in advance for special authorization to pass through the work zone.

Western Construction Inc., of Boise, is the contractor for the $11.2 million project. Total cost of the new interchange, including land acquisition, design, construction and landscaping, will be nearly $20 million.