TERRA Engineering worked with Benesch & Co. to design and analyze options for the redesign of the I-74 / I-155 interchange and adjacent interstate, specifically providing maintenance of traffic analysis and location drainage studies for three proposed alternatives. Context Sensitive Solution was used to design, evaluate, and select the preferred option. Ultimately, a major reconfiguration of the I-74 / I-155 interchange was chosen that involves the lowering of I-74 to the existing grade of I-155 and the raising of I-155 over I-74 at an improved trumpet style interchange.

A location drainage study was prepared as part of Phase I to detail the impact of the proposed improvements and hydraulic modeling was completed for interchange culverts and downstream outlet restrictions in order to establish profile and interchange drainage parameters. Flow patterns were analyzed to determine strategies to mitigate the impact of the proposed developments on the existing waterways of the region.

Extensive maintenance of traffic concepts were developed in conjunction with construction staging and budget parameters. For Phase I, Terra analyzed construction duration, maintenance of traffic cost, and adverse travel costs to compare the three alternatives. For Phase II, once the proposed configuration was selected, a detailed Maintenance of Traffic Plan was developed, including 20 stages and a traffic management plan that prepares the corridor for the anticipated impacts of the proposed improvements on the flow of traffic during construction.


Benesch, Roadway Geometrics Engineer, Structural Engineer, Drainage Engineer
Kaskaskia, Proposed Signage, Proposed Pavement Markings, Erosion Control