Originally opened in 1963, the Brent Spence Bridge and its approaches are key elements of the nation's Interstate Highway System.
The bridge carries both I-75 and I-71 traffic through the Greater Cincinnati and Northern Kentucky area, but it also connects the region to eight other states as far north as Michigan and as far south as Florida.
It is also one of the busiest trucking routes in the U.S., with freight equaling three percent of the nation's gross domestic product (GDP) crossing the bridge each year, according to a 2009 study from the Texas Transportation Institute.
That equates to $417 billion, more than the total GDP of roughly 150 separate countries worldwide.
Originally, six lanes were divided among two driving decks, but renovations in 1986 eliminated the emergency lanes to widen the bridge to four lanes on each deck.
The bridge was listed as "functionally obsolete" by the National Bridge Inventory in 1998, due in large part to limited visibility and safety concerns.
But the replacement project is actually much larger than just the Brent Spence Bridge.
Several miles of highway leading to and from the bridge are also part of the project. This area of roadway will see changes and improvements with the bridge rehabilitation.
The southern limit of the project area is the interchange of I-75 and Dixie Highway (US-127/US-42/US-25) in Kentucky (exit 188). The northern limit of the project is the interchange of I-75 and the Western Hills Viaduct in Ohio (exit 2B). After construction is complete, both of these exits and the span of highway between them would be reconfigured and updated to accommodate new traffic patterns leading to the bridge.