CHICAGO (CBS) — The state is looking to ease traffic congestion at Chicago’s Circle Interchange just west of downtown.

As WBBM Newsradio’s Lisa Fielding reports, the junction is considered one of the worst bottlenecks in the nation. At the site, the Eisenhower Expressway meets the Kennedy/Dan Ryan Expressway, which changes names at the interchange.

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LISTEN: WBBM Newsradio’s Lisa Fielding reports

“Approximately 300,000 vehicles a day pass through the interchange. More than 25,000 of those are trucks,” said Illinois Department of Transportation spokesman Guy Tridgell.

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Tridgell says the interchange is always prone to delays and congestion because of single-lane ramps and tight curves.

“Delays caused by the Interchange average approximately 10 minutes a day per vehicle. That’s a combined 25 million hours of delay annually,” he said.

A $40 million engineering study will explore how to make improvements, and will look at the potential cost and any construction schedule.

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As it is, most of the key components of the interchange have not been altered since they were constructed in the 1950s and ’60s.