Up, down and around: Project continues to solve the squeeze of I-39 and U.S. 20 interchange

The first of two new ramps to aid in the fix of Rockford’s Interstate 39 and U.S. 20 interchange, long hindered by single-lane ramps, sharp curves and an outdated design, opened to traffic Aug. 14. It’s the first major improvement since I-39 first opened in 1984.

“With the new alignment, a safer, more efficient roadway has been created, which will allow an increase of traffic volume and reduce delays in the area,” said District 2 Construction Engineer Matt Hardt.

The new southbound I-39 flyover ramp shifts farther west from the previous one. Motorists travel on a new flyover bridge that straddles both directions of U.S. 20 and is supported by a pair of structural steel box beams weighing 175,000 pounds each. The ramp then continues underneath a new bridge constructed beneath the northbound I-39 to westbound U.S. 20 interchange ramp. Before joining traffic coming from eastbound U.S. 20, the ramp runs through a limestone gorge that runs underneath Linden Road.

The southbound I-39 flyover ramp is part of the larger $98.8 million reconstruction of the interchange that began in summer 2023. The interchange reconstruction project includes 5 new (or reconstructed) bridge structures.  Planning for the interchange began earlier than that.

“This project has been in the works for 20-plus years and has evolved through the years,” said District 2 Studies and Plans Engineer Mike Kuehn. “The main impetus of this project was the high traffic volumes and the fact that the I-39 designation was extended north into Wisconsin in the early 2000s. This requires that the ramps would now need to carry two lanes of I-39 traffic instead of a single lane ramp to U.S. 20.”

In addition, the improvement will bring higher design speeds through the interchange and eliminate broken back curves (two curves in the same direction separated by a short tangent section). Also, the increased lanes and shoulder widths are expected to reduce crashes and traffic delays.

Construction of the new southbound ramp was a challenge given the timeframe to complete the entire interchange in less than two years. The first stage of work included  construction of a new bridge carrying Linden Road across the new southbound I-39 ramp. This stage of work involved excavating a huge trench where the road would be located and blasting through 66,000 tons of rock. Also, the Mulford Road bridge over I-39 was rebuilt to accommodate the new southbound I-39 flyover ramp exit.

Another creative approach employed for the southbound I-39 flyover ramp was the construction of the new bridge that would carry the traffic under the northbound I-39 to westbound U.S. 20 interchange ramp. The work was done without disrupting traffic or closing the existing ramp.

“Designers opted for a `top down’ approach to maintain the flow of traffic and keep the project on schedule,” Hardt explained. “The bridge would be built in a reverse order than what was typical, first having the abutments and then bridge deck built on the existing ground and then perform the center pier substructure work. This allowed both construction operations to proceed efficiently and independent of each other.”

The new southbound I-39 flyover ramp will be opened to two lanes of traffic in a few weeks, and the entire interchange is anticipated to be completed by the end of the year. However, it’s not the end of District 2’s plans for I-39 as the project is part of a larger $247.6 million effort, funded through Gov. JB Pritzker’s Rebuild Illinois capital program, to modernize the interstate through Rockford and Cherry Valley.

“The department as a whole is very happy to see this milestone come to fruition,” Kuehn said. “This is not just a couple ramps but truly a corridor improvement for over 50,000 vehicles per day.”

More information about the I-39 reconstruction project is available on the project webpage.

Click here for more photos and video from the I-39 reconstruction project.

Additional I-39 projects

• Harrison Avenue/U.S. 20 interchange: Work began in April to convert the interchange from a cloverleaf to a diverging diamond design. Completion by the end of 2025, with some final touch-up work to be completed in spring 2026.
• I-39 from the U.S. 20 interchange to Harrison Avenue: Expansion from four to six lanes with an accessory lane and bridge replacements scheduled to begin in 2025. Completion anticipated by the end of 2027.
• U.S. 20 from I-39 to the Kishwaukee River bridge: Expansion from four to six lanes, improvements at Mill Road intersection and replacement of Kishwaukee River bridges scheduled to begin in 2026. Completion anticipated by the end of 2027.

I-39/U.S. 20 interchange facts

• Rock show: The new southbound I-39 ramp required removal of 66,000 tons of rock. The entire interchange project will remove nearly 80,000 tons of rock.
• Heavy metal: A pair of structural steel box beams that are part of the new southbound I-39 bridge over U.S. 20 weigh 175,000 pounds each. Nearly 400 bolts are used for each connection.
• Longer spans: At 484 feet, the new southbound I-39 flyover bridge is 210 feet longer than its predecessor. The span of the new bridge under the northbound I-39 to westbound U.S. 20 interchange ramp is 351 feet.