ISTHA System Wide Interchange Study, Various Locations throughout the Six-County Area, IL

Regina Webster & Associates is serving as a subconsultant to CH2M Hill to provide traffic engineering services for interchange improvements for the Illinois State Toll Highway Authority (ISTHA). The scope of work includes field data collection, traffic forecasting, signalized intersection modeling, data input and calibration of peak hour conditions for the SimTraffic and VISSIM traffic simulation models, and analysis and development of alternatives for operational improvement. RWA is using Synchro to analyze existing nearby signalized intersection conditions and to propose alternatives. In coordination with CH2M Hill and the Tollway staff, RWA is developing operational improvement recommendations for the Tollway and adjacent signalized intersections and control network timing optimization to minimize ramp queues. The parameters of one recommended solution are being entered by RWA into the SimTraffic model. RWA is also entering the required traffic data from manual intersection counts at 100 locations into either the Synchro or VISSIM traffic models as determined to be appropriate by ISTHA.The collected data includes: interchange ramp, mainline, and signalized intersection geometry; dwell time data for peak periods; peak-hour volume turning movements; tollway ramp volumes and cross-street approach volumes. Aerial photo image overlays and information on the control devices and existing timing plans for signalized intersections are also entered into the simulation models.