Drivers heading north on Interstate 17 on the Wednesday before Thanksgiving 2017 were not in for a relaxing “over-the-river-and-through-the-woods” type of trip.
Rather, they faced bumper-to-bumper traffic for miles – up the interstate’s steep switchbacks, and extending north toward Flagstaff.
On that day, Nov. 22, 2017, Interstate 17 traffic peaked at 60,242 vehicles – nearly 10,000 more than the 51,668 vehicles on the same day in 2012, just five years before.
Holidays can be tough for I-17, Arizona’s main north-south route between Phoenix and northern Arizona. Traffic heading north toward the high country tends to clog the interstate for a day or two before a holiday, and then southbound on the day after.
The Arizona Department of Transportation expects another peak or near-peak day on May 25, the Friday before Memorial Day.
But even on a normal Friday afternoon, north-bound traffic often slows to a stop-and-go situation. The same often occurs southbound on Sunday, as the weekend-trippers head home.
Factor in the frequent crashes and roadside fires that occur, and the interstate can become a miles-long parking lot on busy weekends.
State and local transportation experts attribute the problems to a number of factors.
Chris Bridges, administrator of the Central Yavapai Metropolitan Planning Organization (CYMPO), notes that much of the interstate dates back nearly 60 years – beginning in the mid-to-late 1950s, and continuing through the 1970s.
Bridges’ records show that I-17 was the first freeway segment built in Phoenix. The one-mile stretch from Grand Avenue to Thomas Road began in 1958, while the 14-mile segment from Highway 169 to Cornville Road came 20 years later, in 1978.
Although the freeway system in Phoenix has seen many improvements over the years – much of it funded through a half-cent sales tax that is administered by the Maricopa Association of Governments (MAG) – few major improvements have occurred on the northern sections of I-17.
Arizona State Engineer Dallas Hammit says that is largely due to the difficulty of coming up with the large sums of money that would be needed to make a difference on I-17.
“It is such a big project,” he said. “From Black Canyon City to Cordes Junction, we were looking at $600 million. That’s a big lift.”
Meanwhile, he said, “There is not a lot of interim work that helps us on this.”
In addition, he pointed out that the Arizona Department of Transportation (ADOT) has faced many needs on its highways in recent years. Much of the priority in the Prescott area in the early 2000s focused on Highway 89A and Fain Road improvements.
“That would have been a competing priority,” Hammit said. More recently, the state has devoted millions of dollars to widening Highway 89 north of Prescott.
One of I-17’s main challenges is its dramatic change in altitude. From Phoenix’s 1,117-feet elevation, to Flagstaff’s 7,000 feet, the highway climbs nearly 6,000 feet in its 145-mile length.
Dealing with widening projects on the steep terrain north of Black Canyon City adds to the costs.
“The immense expense always made this a big challenge,” said Doug Nintzel, ADOT spokesman. “The mountainous, winding section of highway is a big factor there.”
The switchbacks have also proven problematic for drivers.
ADOT District Engineer Alvin Stump reports that between October 2016 and October 2017, 172 accidents occurred on I-17 between Anthem and Sunset Point.
Those accidents typically close down one side of the freeway for a time – sometimes causing traffic to back up for miles.
Just in the past several weeks, several major road closures occurred on the interstate.
On March 17, for instance, ADOT cautioned motorists heading north that evening to plan for delays in Black Canyon City. The reason: A crash that had caused a four-mile-long traffic backup. ADOT’s initial notice came out at 4:38 p.m., and it was nearly two hours later that the department sent another notice, stating that all lanes were open, but that significant delays were still expected.
Then, on March 23, ADOT announced that a brush fire had closed southbound I-17 about 20 mile south of Cordes Junction. Although the interstate was partially reopened about an hour later, ADOT cautioned: “Drivers should still expect heavy delays in the area and consider delaying travel south of Cordes Junction until the entire highway opens.”
Growing Traffic Load
Compounding I-17’s problems is a steady increase in traffic.
“Last year was the first time we started seeing the 60,000 numbers,” Stump said. Just five years ago, a typical peak traffic number was in the 45,000 to 50,000 range, he said.
Since then, traffic numbers have grown dramatically – by 6 percent in 2015; 5 percent in 2016; and 8 percent in 2017.
Hammit said traffic increases have been reported on other state highways as well. He guessed the increases were the result of a combination of factors, including an improved economy and relatively low gas prices.