Signal timing an issue on Carefree Hwy
by Kathleen Stinson

NORTH VALLEY – For commuters burdened with growing congestion at major Carefree Highway intersections, traffic‑signal timing is crucial to reducing backups.

Although the county is expected to soon roll out recommendations for widening the highway by adding one lane in both directions, local jurisdictions that control the intersections are, in the meantime, paying more attention to adjusting signal timers and planning additional turn lanes.

Scottsdale adjusted the timer at the Scottsdale Road/Tom Darlington Drive intersection last week, and Phoenix recently added left‑turn lanes to Carefree Highway at 27th Drive near Tramonto. Cave Creek is currently studying the signal timing and designing an additional left‑turn lane from northbound Cave Creek Road onto westbound Carefree Highway.

“Signal timing is a critical element of congestion mitigation,” said Eric Anderson, transportation director for Maricopa Association of Governments.

“In theory, signal timing is designed to minimize delay of motorists in all directions.”

But if one arterial at an intersection is the dominant flow of traffic, the green light in that direction can be extended to favor that traffic flow, Anderson noted.

Many North Valley roadways have sensors that vary the duration of a green light, depending on the number of cars at the intersection. The intersections of 7th Avenue and 27th Drive with Carefree Highway allow the light to continually shine green until sensors on those side streets indicate the presence of a vehicle.

According to City of Scottsdale signal analyst Steve Ramsey, the Scottsdale Road/Carefree Highway intersection contains roadway sensors which permit the light to stay green from six to 24 seconds. The last time the city changed that signal timing was in 2003, he indicated. However, in response to a call last week from The Desert Advocate, the city extended the eastbound green light by 25 percent.

“People will call up,” Ramsey said. “If we can, we will adjust the timing, but we have to take it away from the other direction. Most of the time we can make small adjustments.”

In the case of the recent Scottsdale Road change, Ramsey said extending the green light does not affect north‑south traffic flow.

Cave Creek recognizes the need to address traffic congestion at the Carefree Highway/Cave Creek Road intersection, and  the town is in the process of designing an additional left‑turn lane for northbound traffic turning west.

“That left‑turn lane can back up almost a quarter of a mile during peak hours,” said Souren Naradikian, assistant town engineer, noting the project will be let out for bid soon after the design is complete.

Engineering consultants Mantri & Assoc. LLC have recently started a feasibility study on behalf of Cave Creek, looking at signal timing and any need for additional left‑turn lanes.

About a year ago, the town changed the timing of the northbound left‑turn signal at Carefree Highway to the maximum number of seconds, said Steve Poole, traffic supervisor for Maricopa County Department of Transportation.

But Poole also points out that signal timing has its limitations. Adding seconds in one direction can back up traffic in the other direction, requiring another extension of that signal and so on.

Cameras at some Valley intersections allow traffic‑signal analysts to change the timers to adapt to the flow of traffic throughout the day.

It’s no secret: Traffic is increasing in the North Valley.

According to 2006 statistics provided by MCDOT, about 21,000 vehicles per day travel Carefree Highway between 32nd and 48th streets, not far from the Cave Creek Road intersection. That number is projected to grow to 33,000 vehicle trips per day by 2026. An average 15,000 vehicles per day travel between 60th Street and Scottsdale Road.

Traffic controls at the Carefree Highway/7th Avenue and 27th Drive intersections are under the jurisdiction of the City of Phoenix. An average of 21,000 vehicles per day travel the highway between 7th Avenue and 23rd Lane, according to MCDOT. The county projects traffic volumes to increase to 37,000 vehicles daily by 2026.  

Phoenix traffic management supervisor Joel Havris said the city has not changed the signal timing at 7th Avenue since 1999.  The timing at 27th Drive remained the same when, in September, the city added left‑turn arrows.

“The city added the arrows to enhance the traffic flow, with all the growth and demand for turns. The demand is definitely there,” Havris said.

Those Carefree Highway green lights remain on until sensors on the side streets detect the presence of vehicles intending to enter the highway, according to Havris. Eastbound and southbound vehicles are guaranteed a minimum of 34 seconds of uninterrupted green at 7th Avenue and 30 seconds at 27th Drive. This signal configuration the city refers to as a free operation.