Route 109 Widening and Roundabout
HR Green designed this federally funded project that widened Route 109 from 2-lanes to 4-lanes, added two multi-lane roundabouts, and two trail grade separation structures. A VISSIM traffic simulation model was developed to assess traffic operations along the corridor, including between the roundabouts and at the interchange ramp terminal of westbound Route 100.
Access management between the interchange and destinations along the corridor was enhanced by the roundabouts and their capability for U-turn maneuvers. One pedestrian structure is a single-span, 90-foot long prefabricated steel truss and the other is a precast underpass with MSE walls. The project won several awards in 2015 including an ACEC Honor Award and the APWA St. Louis Branch Project of the Year.