green arrow

Leading or lagging left green arrows? The choice comes dow to safety, officials said.

SIERRA VISTA — You may have noticed that the left-turn arrow onto Buffalo Soldier Trail off northbound State Highway 92 on Sierra Vista’s south side was recently changed from a lagging signal — coming after the light for through traffic turns red — to a leading signal — coming before the light for through traffic turns green.

We know at least some have noticed the change, because City of Sierra Vista employees assured the Herald/Review that they have heard from several residents who want to know why that left-turn arrow, along with at least one other in the city, was switched from lagging to leading.

The answer to that question is rather simple, though it doesn’t come from the City of Sierra Vista. Rather, the Arizona Department of Transportation has dominion over all traffic signals on state highways, such as the one at Highway 92 and Buffalo Soldier Trail.

Asked about the change at that intersection and planned switches for other state highways in Sierra Vista, ADOT Assistant Communication Director for Public Information Steve Elliott said “the reason for this change comes down to safety.”

At each of their stop lights, ADOT assesses the best options based on local conditions, Elliott said.

Their lights in Sierra Vista mirror conditions in an area north of Tucson along Oracle Road, where “changing to leading left-turn arrows has reduced crashes,” Elliott explained.

Traffic signals within city limits that are not on state highways fall under the jurisdiction of the City of Sierra Vista, which can decide if they want leading or lagging left-turn arrows.

Sierra Vista has traditionally had lagging left-turn arrows, said City Engineer Jing Luo, who basically stated that the city is taking the “if it isn’t broken, why fix it?” approach.

“We haven’t had any issues with our system within the city ... we’ve been pretty successful with the way that we have (been doing it),” Luo said. “We haven’t had many complaints from the public. I’m not saying it won’t happen, but so far, so good.”

Luo said the city, when making any kind of change regarding traffic signals, goes through an intensive process that studies potential impact of such changes and requires committee approval. Key to making any changes that the public might notice, she said, is communication.

“Change without good communication with the public will potentially lead to accidents,” Luo said.

She illustrated that thought with a hypothetical about someone who drives the same way home every day, going through the same stop lights.

Eventually, their drive becomes a matter of habit and if a turn arrow is changed from lagging to leading, or vice versa, one day without their knowledge, they could get into an accident because their driving habits take charge and they could drive right through a red light.

So, as ADOT has updated its signal cabinets in Sierra Vista to leading left-turn arrows, Luo said the city is doing all they can to help inform the public about the switch through the city’s website and social media pages.

“Even if it’s not our responsibility, like with the highways, I still feel it’s our job to help (ADOT) do a better job (informing people),” she said. “It’s our city. Personally, my philosophy is to take 100 percent responsibility for our own community.”

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