Design of new Tucson interchange promotes efficiency and safety

TUCSON ‒ It may not be immediately apparent to those using the busy interchange of Interstate 19 and Ajo Way (State Route 86), but a single set of signals will soon control traffic in a configuration designed for efficiency and safety.

I-19 and Ajo Way soon will become the Arizona Department of Transportation’s third single-point urban interchange in the Tucson area. Others are at I-19 and Valencia Road, and at Kino Parkway and State Route 210 (Barraza-Aviation Parkway).

“We have an opportunity at Ajo Way and I-19 to use a design that allows traffic to move more efficiently through the intersection more quickly because drivers only have to move through one set of lights instead of two,” said James Gomes, regional traffic engineer for ADOT’s South Central District.

Temporary signals are in place at Ajo Way at this time. The new signals are scheduled to begin operating in January.

Created in 1974 in Clearwater, Florida, the design is often used when an interchange is being reconstructed. In a single-point urban interchange, left-turn drivers from opposite directions can move through the intersection at the same time. Among its other benefits, the design accommodates larger vehicles, including trucks and recreational vehicles, even better than traditional diamond interchanges.

This design has safety advantages as well. While the rate of collisions is about the same, the single-point urban interchange has a lower rate of injuries and fatalities.

After crews poured the new bridge deck over last weekend, the first phase of the project, which also includes widening Ajo Way and improved exit ramps at Ajo Way and Irvington Road, remains on schedule for completion in the spring. The second phase, which hasn’t yet accepted bids from potential contractors, will include widening southbound I-19, an additional transition lane for northbound traffic between Irvington and Ajo Way and improvements on Ajo Way that include a new bridge over the Santa Cruz River.