At peak periods, thousands of vehicles, pedestrians and cyclists make their way hourly through the East Speedway-North Campbell Avenue intersection, at the northeast corner of the University of Arizona campus

As with many intersections in the city, drivers who have to turn left have a shot during the through traffic cycle — if there’s a break in oncoming vehicles — and another with a dedicated arrow after that cycle ends. That’s known as permitted/protected phasing.

Some local officials, including Tucson Police Department Assistant Chief Kevin Hall, say that setup can be dangerous for both motorists and pedestrians, who might not be noticed by drivers scoping an opportunity to turn. There have been six pedestrian-involved collisions, five bicycle-involved collisions and 79 traffic incidents — none fatal — at or near the intersection since mid-2012, according to city GIS data available online.

“The vast majority of intersection crashes at red lights are due to permissive left turns,” Hall said.

So, if not the current setup, then what?

The university-area intersection will play host to one alternative — a protected left — likely beginning early next year. A protected left simply means drivers are able to make that turn only when they have a green arrow. There are some such intersections in city limits, but few — if any — at a traditional arterial intersection, according to a transportation official. The switch will cost around $25,000, which doesn’t include the staff time necessary for the before-and-after studies.

Starting this fall, the Tucson Department of Transportation will begin gathering before data to be able to evaluate the change’s impact on collisions, traffic flow, volumes and other metrics.

While conceding that the protected left could reduce the potential for some collisions, Andy McGovern, TDOT’s traffic engineering administrator, said he “expects to see an increase in traffic delay,” as well as a possible increase in red-light running and some kinds of minor accidents, like fender-benders.

On TDOT’s website, protected left’s are criticized as “very inefficient” and a cause of capacity reduction and increased congestion. As it stands, the average driver spends 50 seconds at the intersection during peak periods, according to McGovern.

But Councilman Steve Kozachik, who has been pushing for the pilot project, said that what he described as minimal additional delays are worth the increased safety offered by protected lefts. If the study results are positive, he’s hoping protected lefts become “standard operating procedure” for Tucson arterial intersections with high traffic and pedestrian volumes.

As to the additional delays, he said they would likely be measured in “seconds, not minutes.”

“People can take a few more seconds to get home safely, and you’re certainly going to take a lot longer if you end up T-boning somebody,” he said.

TDOT, on the other hand, says it’s hoping to move toward a modified approach to the permitted/protected phasing in which left-turners have a flashing yellow light when the through traffic has a green light to encourage additional caution. In fact, McGovern said his department is drafting a policy to convert intersections with left turn arrows to flashing yellow arrows, and a number are already in place.

Close to the UA campus, several of those signals actually switch to a protected left when there are more pedestrians during the day and back to a flashing yellow in the evening, something McGovern described as one of the city’s “first forays into adaptive traffic-signal control.”

Kozachik takes a dim view of the flashing yellows and part-time protected lefts, arguing that a full-time protected left is “simpler.”

But in a town like Tucson without the freeway network of Phoenix, where protected lefts are fairly common, McGovern said efficient flow is more important because many motorists get from one end of the city to the other on arterials.

“We’ll find out during the course of next year if those delays acceptable to the motoring public,” he said of the upcoming Speedway-Campbell pilot project.

DOWN THE ROAD

Starting Tuesday, the Pima County Department of Transportation will begin microseal treatment of West Ruthrauff/Wetmore Road from North La Cholla Boulevard to North Fairview Avenue. Preliminary work will last through Monday, Sept. 18, with shifts lasting from 5 a.m. to 6 p.m. The treatment will start Oct. 9 and last through Oct. 18. During the work, lane restrictions and reduced speeds will be in effect. Sheriff’s deputies, flaggers and a pilot car will be on hand.

Contact: mwoodhouse@tucson.com or 573-4235. On Twitter: @murphywoodhouse

Pima County reporter and Road Runner columnist for the Arizona Daily Star