Project Description

Diverging Diamond Intersection Design Study

Diverging Diamond Intersection Design Study
  • LOCATION: Marion, IL

  • CLIENT: IDOT D9 / City of Marion, IL

Project Description:

This project consisted of the reconstruction/ reconfiguration of the existing partial diamond interchange (Morgan Avenue (renamed: The Hill) over I-57) as a complete Diverging Diamond Interchange – the first in the State of Illinois at the time of construction. Morgan Avenue is access controlled throughout the project limits.

Scope of Work:

Morgan Avenue (renamed: The Hill) in Marion, IL was reconfigured to a Diverging Diamond Interchange.  A DDI is different from other Diamond Interchange configurations in that the two directions of traffic on the minor intersecting roadway cross to opposite sides at the ramp intersections.  The advantage is the ability to remove left-turn movements from the intersections of the ramps and minor roadway creating a free flow condition for these movements.  It also reduces the required signal phasing to two phases, resulting in a more efficient flow of traffic.

TWM provided feasibility investigations, traffic modeling, trip generation report, and preparation of IDS’s.  TWM also traffic analysis for different intersection types, finalizing on realigning the sideroads Shane Lane and Stanford Lane into one large signalized intersection to provide future development access.

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