The I-75/I-575 Managed Lanes Extension Project, also known as the Northwest Corridor Project, improved travel in the I-75/I-575 corridor by adding 29.7 miles of toll lanes along I-75 from Akers Mill Rd to Hickory Grove Road and along I-575 from I-75 to Sixes Road. Two express lanes were built to the west of the existing lanes along I-75 between I-285 and I-575. From that interchange, one express lane was added along I-75 north to Hickory Grove Road and one express lane was added along I-575 to Sixes Road. The project reduces congestion, improves mobility and safety, and reduces vehicle emissions.

This Georgia Department of Transportation Design-Build project included many bridges and several tunnel-like bridges. H&L was heavily involved in the pre-bid bridge design for the contractor, designed 15 bridges along the corridor of this fast-track project, and provided construction engineering services. The bridge portion of the corridor included design for widening of existing bridges and design of multiple new bridges that consisted of steel curved girders, long spans, complex structures, post tensioned straddle bents, and pile bents.

The bridges designed by H&L included:

• I-575 Managed Lanes over I-75 Managed Lanes and I-75 – a curved, four-span, continuous steel ramp bridge that was built within the existing interchange.
• I-75 Managed Lanes over Barrett Parkway, I-75 southbound and I-75 southbound On-Ramp – an 11-span structure that utilizes a 65 foot long, precast, post-tensioned straddle bent over I-75 and the longest Bulb Tee PSC beam span in the state of Georgia.