Hamilton County commissioners have hired Gradex to build a new roundabout beneath an elevated 146th Street at Hazel Dell Parkway, with construction starting this fall and continuing through 2029. The $39.9 million project sits on the border of Carmel and Noblesville, at an intersection county officials say has a high crash rate.
The timing is notable: commissioners awarded the Hazel Dell contract on the same day officials cut the ribbon on the newly finished 146th Street and Allisonville Road interchange, according to WISH-TV. That $44 million Allisonville project, located on the Fishers-Noblesville border, replaced a traffic signal with a roundabout-and-overpass combination and ranks among the largest infrastructure investments in Hamilton County government history, per the same report. Brad Davis said the completed Allisonville interchange “gives people a good idea of what we're working toward at Hazel Dell,” adding that the projects address congestion in a way that will serve the corridor for decades.
Why an Overpass Instead of a Signal
The push for a grade-separated design at Hazel Dell traces back to a 2021 traffic analysis in Hamilton County's environmental assessment, which found westbound 146th Street operating at a Level of Service F — a rating denoting heavy congestion and operational failure during peak hours, according to the Hamilton County Environmental Assessment. Engineers designed the new interchange to bring that rating back up to Level of Service C or better through 2046. Preliminary design work for the split-level roundabout was handled by Westfield-based Butler, Fairman & Seufert Inc. and Indianapolis-based CHA Consulting Inc., the Indianapolis Business Journal reported.
State environmental filings show the project footprint spans 2,200 feet east and west along 146th Street and up to 650 feet north and south along Hazel Dell Parkway, requiring roughly 4.46 acres of land acquisition. The plan includes a 291-foot bridge carrying 146th Street over the roundabout below, per the same assessment. Funding for the work includes an $8.7 million grant from the Indianapolis Metropolitan Planning Organization, while the county is covering the remaining $39.9 million contract cost with Gradex, a Carmel-based company, according to WISH-TV.
Part of a Longer Corridor Strategy
Hamilton County has been expanding 146th Street into a primary east-west arterial for nearly 25 years, including a 2007 extension that connected the road to Interstate 69 at Exit 10, the Indianapolis Business Journal notes. The Allisonville interchange received about $9.5 million in federal funds, with the remainder coming from local government sources, per WISH-TV. Planning is already underway for a third link in the chain: the Indianapolis Metropolitan Planning Organization has awarded $6 million to begin design work on a similar roundabout interchange at 146th Street and Gray Road, near the Carmel-Noblesville-Westfield border, with construction potentially starting in 2029.
Roundabouts are hardly a novelty in this corner of the state. Hamilton County counted 284 of them across its municipalities as of 2025, with 157 in Carmel and 47 in Noblesville, according to Visit Hamilton County. Carmel in particular has built a national reputation as the self-styled “Roundabout Capital of the United States,” having constructed more than 150 roundabouts since 1996 and cut its signalized intersections down to just 15, per WZBD. Academic research cited by Purdue Fort Wayne civil engineering faculty in 2024 found that converting signalized intersections into roundabouts in Indiana cuts overall crashes by roughly 40%, injury crashes by 44%, and fatal crashes by 70%, the outlet reported.
Lessons From a Rougher Rollout Nearby
Not every roundabout conversion in Hamilton County has gone smoothly. After a multi-lane roundabout opened at 96th Street and Allisonville Road in neighboring Fishers in October 2024, an immediate spike in collisions prompted the city to add extra lighting and signage and scrap plans for a similar roundabout at 116th Street in favor of standard lane improvements, as Hoodline previously reported. That history underscores why the design for 146th and Hazel Dell keeps things separated rather than blended at one grade.
Design plans for the new interchange route all pedestrian and bicycle crossings across the lower-speed Hazel Dell Parkway and its connecting ramps, keeping non-vehicular traffic off the high-speed 146th Street overpass entirely, according to The Hamilton County Reporter. The layout is meant to connect local pedestrian trails without ever forcing a crossing of the elevated corridor. The buildout of this stretch has included bridge widening and roundabout preparation on the Allisonville segment.
