Airport Road & IL Route 126 Stevenson Expressway (I-55) Interchange Phase I
The six-mile stretch of the Stevenson Expressway (I-55) between US Route 30 and Weber Road only had one interchange, consisting of a northbound on-ramp and a southbound off-ramp. In accordance with NEPA requirements, our team provided Phase I engineering services for two full-access interchanges in Will County, IL. Our services included traffic projections, traffic modeling, geometric studies, interchange and intersection design studies, access justification report, environmental assessment, combined design report, traffic management analysis, bridge condition evaluations, and location drainage study. The preferred build alternative included a new full access interchange at Airport Road and a reconfigured interchange at IL 126, providing full access.


Market Sector
TransportationPrimary Service Lines
Highways & Traffic, Resilient Water Solutions, StructuralRegion
ChicagoAdditional Info
Project Highlights:
- Key challenges included modifying an existing partial interchange to provide full access in both directions, in a corridor surrounded by wetlands.
- Study limits included 3.5 miles of I-55, one mile of Airport / Lockport Road, one mile of IL Route 126, a half mile of Essington Road, and a half mile of 135th Street.
- The corridor also included Section 4(f) properties as well as other sensitive environmental issues involving noise, water quality, flooding, wetlands, special waste, and traffic impacts which were documented in an environmental assessment.
- We also conducted bridge condition evaluations for three structures: two that cross the expressway and one that traverses Lily Cache Creek, for which we also performed a hydraulic analysis to design the waterway opening for the creek under Lockport Road.
- Phase I engineering services also included the preparation of a combined design report, interchange type study, updated access justification report and location drainage study.
- The project also featured an extensive public involvement program which follows the principles of IDOT Context Sensitive Solutions procedures. To date, this program has included a stakeholder involvement plan, community context audit report, three public meetings, six community advisory group meetings, a project website and local government official briefings.
Related Projects

Tri-State Tollway (I-294) Widening & Rehabilitation
Our team was the lead design firm of the Illinois Tollway’s $4 billion improvement of the Central Tri-State Tollway (I-294), an ambitious project …

300 S. Tryon Outdoor Terrace Garden
High above Uptown Charlotte sits a stunning 8,000 square foot rooftop deck, providing beautiful, 180-degree panoramic views of South End and BB&T …

Old Post Office Mixed-Use Redevelopment
The Old Post Office in Chicago is a national historic landmark, built in 1921 with many renovations over the course of its 100 years.

Edmonton Metropolitan Region Board
Edmonton Metropolitan Region Board (EMRB) is made up of 13 municipalities that are required to align with multiple regional policy documents that …