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  • Illinois Department of Transportation

Interstate 255 is a 30-mile long bypass route that runs through Missouri and Illinois. Due to the very poor condition of the pavement and bridges in various stretches of the roadway, a major rehabilitation was necessary and the Department decided to investigate a complete closure of the interstate to reduce the construction duration from 4 years to 10 months, save taxpayers nearly $14 million, provide safety to the traveling public by eliminating lane shifts, reducing accidents and driver confusion and to ensure safety of workers during construction by keeping traffic out of the work zone.

Oates Associates was brought on board for the section of I-255 from IL Route 15 interchange to the I-64 interchange. We began by preparing a traffic study showing “hot spot” locations and the overall volume-to-capacity (v/c) ratios before and after the closure. Oates analyzed conditions for routes seeing an increase in traffic due to the closure, which included a pavement condition survey of routes and inspection of railroad crossings and ramps. Highway Capacity Manual (HCM) models were prepared and aided with suggesting improvements to the “hot spot” areas. The goal of the project was to determine what modifications are needed to accommodate the anticipated increase in traffic while preserving existing infrastructure. The Department reviewed the traffic study and determined that complete closure was a feasible alternative and Oates proceeded to preparing preliminary and final plans.

The roadway improvements consisted of pavement repair details on mainline and ramps, drainage modifications and improvements, guardrail warrant analysis and replacement, pavement modifications to address vertical clearance deficiencies, concrete median replacement, bridge approach re-profiling, maintenance of traffic plans, ADA upgrades at ramp sidewalks, and erosion control plans.

The bridge work included the preparation of plans, specifications, and estimates for the rehabilitation of five dual interstate bridges, two overpass bridges, and various sign trusses. We worked closely with IDOT personnel to inspect the bridges and establish repair needs. Scope of bridge work included joint replacements, deck patching, bituminous overlay, integral abutment conversions, steel girder plating, steel bearing stiffener replacement, steel diaphragm replacement, steel painting, pedestrian rail repairs, bearing seat repairs, end slope erosion mitigation, wingwall replacement, and substructure concrete repairs.

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