The traffic flow design is credited to Mexican engineer Francisco Mier.

The Utah Dept. of Transportation on Sept. 18 opened the state's first continuous flow intersection (CFI) at 3500 South and Bangerter Highway, just south of Salt Lake City. The $7.5-million, seven-month project entailed new signals, medians, striping and concrete paving. Western Quality Concrete, Springville, Ut., was the general contractor, with Cater & Burgess' Salt Lake City office as engineer. Fehr & Peers, Salt Lake City, was the conceptual engineer. The congested four-way intersection in West Valley City sees about 100,000 cars daily, with drivers waiting up to four light signal cycles to get through the intersection.

The CFI shifts left turns from Bangerter Highway onto the far left of 3500 South for 11% more green light time. Left turns are set back about 200 ft so while oncoming traffic is stopped, left turners will cross the oncoming lanes to a far left turn lane at the main intersection. Since they have already crossed the lanes of oncoming traffic, drivers will turn left onto 3500 South at the same time that through traffic is also moving for an estimated 31% increase traffic flow and 50% reduction in wait time, officials claim.


CFI Traffic Simulation (Credit: UDOT)

"This concept is new to Utah and looks a little different than a traditional intersection, but most drivers will find it to be safe and easy to navigate," said Randy Park, director of UDOT Region 2.

The CFI will be the first intersection of its kind in Utah, as well as the western U.S. Originally designed in Mexican engineer Francisco Mier, CFI has since been implemented in Louisiana, Maryland and New York with positive results. At the intersection in Baton Rouge, La., where CFI was introduced, the average wait time was reduced from 4-min. to less than 1-min. Depending on the results at 3500 South and Bangerter Highway, UDOT may implement CFIs at other locations in the future.