Since its completion in April 2017, the Dallas Horseshoe interchange has substantially improved the flow of traffic crossing the Trinity River along Interstate 30 and Interstate 35 to enter or exit the Texas city’s downtown.
The $798 million interchange replaced a notoriously complex maze of tricky interchanges, bridges and roadways in downtown Dallas known as the Mixmaster interchange.
The original intersection was state-of-the art when it first opened in 1964, but it gradually developed an unfortunate reputation as a site of frustrating bottlenecks, lengthy traffic delays and safety concerns. By the time design work began in 2013 on a complete interchange replacement, the Mixmaster was deteriorating and ill-equipped to handle the estimated 450,000 to 500,000 vehicles that pass through on a normal weekday.
The Mixmaster’s left-lane exits and odd geometry created a lot of weaving in and out of the lanes. Correcting the Mixmaster’s confusing alignments was one of the highest design priorities. The Dallas Horseshoe eliminated all left exits, providing direct connections from northbound I-35 East to westbound I-30, and eastbound I-30 to southbound I-35 East.
As the lead engineer, WSP was responsible for planning the complete removal and methodical replacement of the Mixmaster interchange, as well as the replacement of the I-30 and I-35E crossings over the Trinity River. The firm’s responsibilities included design of roadways, bridges, river crossings, retaining walls, drainage, geotechnical engineering and maintenance of traffic planning.
WSP teamed with Pegasus Link Constructors (PLC)—a joint venture of Fluor Enterprises and Balfour Beatty—for the design-build contract to create the Dallas Horseshoe on behalf of the Texas Department of Transportation (TxDOT). Construction began in January 2014.
The Dallas Horseshoe is about 80 percent elevated roadway. The project included the construction of more than 73 lane miles of new roadway, 37 conventional bridges and more than 60 retaining walls.