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Why does Tucson have so many different kinds of left turns?

Posted: 6:24 AM, Oct 26, 2021
Updated: 2021-10-28 12:54:00-04
Flashing yellow arrows are just one type of left turn drivers see around Tucson.

TUCSON, Ariz. (KGUN) — For drivers in Tucson, just making a left turn can look very different from one intersection to the next.

There’s lagging arrows, and leading arrows and flashing yellow arrows. Even intersections with no left turns at all—the so called ‘indirect’ or ‘Michigan left,’ which involves a U-turn once past the intersection.

While the variety of options can be confusing, the city says it’s all in the name of safety.

“So basically, not every intersection is the same,” said Greg Orsini, traffic engineering manager with Tucson’s Department of Transportation and Mobility. “There could be different geometric conditions.”

Orsini says the different left turn lights are tailored to each individual intersection to make them safer and less congested.

“And so, that’s why it really comes back to the basics,” Orsini said. “You see your green movement, that’s your movement. You see the yellow, you can proceed with caution. And when there’s the red, that’s when you stop because the other directions are traveling.”

Tucson DTM says about 80 percent of the city’s intersections with left turns have ‘lagging’ left turns—arrows after the green light—which Orsini says have been known to be smoother and safer.

“The lagging allows for clearance of the through movements, and then the left turn movements make their move, and all the pedestrian movements have cleared at that time,” he explained.

Orsini says leading arrows are sometimes “a little better for the operations,” usually in ’T’ intersections or where “one direction has a much higher traffic volume making that left turn movement than the opposing direction.”

The flashing yellow lights have been confusing for some drivers, but Orsini says they have an extra benefit.

“It’s yellow, so someone can cautiously make their left turn movement when there’s a gap in traffic,” he said. “However, if a pedestrian pushes a push button, the arrow will remain red and the pedestrian will be able to make their crossing movement without any potential conflict from a vehicle.”

The indirect lefts are on Grant Road and are relatively new. Orsini says they’re a good fit for wide streets with high traffic volumes, because they naturally keep cars flowing past the intersection. Those looking to make a left can U-Turn soon after the intersection to avoid building up a line of turning cars at the intersection itself.

A DTM study found the indirect left at Grant Road and Oracle Road reduced crashes by more than 70 percent when comparing three-year stretches before and after construction on the intersection was complete.

Data shows the indirect left at Grant Rd. & Oracle Rd. significantly reduced crashes at the intersection.
Data shows the indirect left at Grant Rd. & Oracle Rd. significantly reduced crashes at the intersection.

However, Tucson Police data from 2018-2019 found left turns were the leading cause of crashes in intersections around the city, specifically identifying the 10 most common sites for crashes.

Some drivers say the lack of left turn consistency in Tucson is inherently confusing. Orsini’s advice is to slow down and focus.

“Pay attention to what’s around you,” he said. “Pay attention to your surroundings. Follow that speed limit. Pay attention to the traffic controls that are up.”