SH 121/US 75 Interchange in Collin County, TX, NTTA

IEA provided overall QA/QC and PS&E for traffic control plans, removal plans, and SW3P as task leads along with design support roles in other roadway and structural design tasks and public involvement for this interchange. IEA utilized the existing and proposed guide signs for the maintenance of traffic during construction, which avoided the duplication of large guide sign structures. This project also required tremendous amount of coordination due to the large number of stakeholders in a smaller area. The stakeholder included NTTA, TxDOT, cities of McKinney and Allen, and Town of Fairview. The $220 million interchange consists of reconstruction of 4-miles of existing SH 121 from a 4-lane divided section to a 6-lane divided section (toll road) and 2-miles of US 75 from a existing 6-lane divided section to an 8-lane section including provisions for future managed lanes. The project included 26 ramps, 8 direct connectors, 3-lane frontage roads along SH 121 and US 75, and 5 diamond interchanges.