ARIZONA, USA — The most treacherous stretch of highway in Arizona is right here in the Valley.
Interstate 10 at mile markers 144, 145, and 146 saw more accidents than any other part of Arizona roadways in 2020, according to data provided by the Arizona Department of Transportation.
The three-mile stretch approaches the major junction where I-10, Loop 202, and State Route 51 meet.
In an email, ADOT said:
"I-10 in the area of the SR 51/Loop 202 "Mini-Stack" interchange is among the busiest stretches of Valley freeways. Traffic volume and merging heighten opportunities for drivers to be involved in crashes."
"It’s not that surprising to me," Ram Pendyala, director of ASU’s the School of Sustainable Engineering and the Built Environment, said. "Whenever you have three major arteries come together it’s a very complex situation."
"Stacks" are when multiple freeways are layered on top of each other. The idea is to provide an efficient system to get drivers to major highways.
However, the more roads and ramps there are the more potential issues.
“The moment you add a third or a fourth [road], the number of ramp connections really increases exponentially. And you are going to have more conflict points as people weave in and out,” Pendyala said.
Those conflict points can lead to crashes. According to the data, 2020 saw more than 1,000 crashes near these mile markers.
So why do cities build these junctions? Pendyala believes it comes down to money and space.
"Sometimes in major metropolitan areas, you can’t avoid it,“ Pendyala said.
According to the professor, it is cheaper to build one major junction than multiple interchanges. Also, in a city where space is a premium resource, these "stacked" junctions can take up a smaller area.
Pendyala said a reason for the high number of crashes could be related to the rapidly rising population in the Valley.
"The way the Valley has grown and the region has grown," Pendyala said "Probably far greater than what the original projects were."
Pendyala said after a junction is built, making large changes can become difficult and expensive.
“I think it’s worth looking into and doing a deeper dive into the data to understand what type of crashes are these,“ Pendyala said.
See other I-10 trouble spots on the map below
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