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Key Facts
SR-347 carries more than 31,000 vehicles per day (ADOT project data). Nearly all of them funnel through the I-10 interchange.
Speed differential at the merge is the primary crash factor. Freeway speed meets commuter queue backup within a few hundred feet.
Commercial trucks are a growing component of SR-347 traffic as logistics and distribution operations expand in Maricopa and Casa Grande. Heavy vehicles need more stopping distance and more lane room than the interchange geometry provides at peak volumes.
ADOT awarded the $396M SR-347 widening to Sundt Construction in early 2026. Pavement rehabilitation started summer 2026. Widening and interchange construction begins winter 2026-2027.

The SR-347 and I-10 interchange is the single piece of infrastructure that decides whether tens of thousands of Maricopa residents get to work on time.

It’s also where a disproportionate share of Pinal County’s serious crashes happen.

Two corridors meet at one merge. Both operate above design capacity during peak hours. The crash data is the predictable result.

SR-347 carries more than 31,000 vehicles per day per ADOT project data, nearly all funneling through the I-10 interchange at the edge of design capacity
Daily traffic volume on SR-347 through its interchange with I-10, per ADOT data.

Source: Arizona Department of Transportation, SR-347 Improvement Project (azdot.gov/sr347).

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31,000+
Vehicles per day on SR-347 per ADOT project documentation, nearly all funneling through the I-10 interchange
ADOT SR-347 Improvement Project (azdot.gov/sr347)

The Geometry of the Problem

SR-347 is a two-lane divided highway for most of its run between Maricopa City and I-10, then expands modestly at the interchange approach. I-10 at this point is a full interstate carrying long-haul freight between Tucson, Phoenix, and the Southwest.

When SR-347 traffic hits the interchange, the lane patterns force quick decisions. Drivers heading to Phoenix need the eastbound I-10 on-ramp. Drivers from I-10 headed to Maricopa need the southbound SR-347 exit. Local traffic threads through both. Commercial trucks make wide turns that eat shoulder space.

The design works when traffic is light. It doesn’t work at rush hour.

The Speed Differential Problem

Here’s what most people don’t account for. Approaching the interchange from the north on SR-347, drivers are at or near the 65 mph posted speed. Once queue backup starts, traffic transitions from 65 to 10 within a few hundred feet. The driver three cars back doesn’t see the brake lights until the gap closes.

Rear-end at a speed differential of 40 mph is a major-injury crash. When a commercial truck is in the chain, it’s a multi-vehicle event.

This pattern shows up in the broader SR-347 corridor data. The interchange concentrates the problem.

The Truck Factor

Commercial traffic on SR-347 has been growing as distribution and logistics operations expand in Maricopa and Casa Grande. No published ADOT source provides a current truck-mix percentage for this corridor, but the growth in regional warehousing and freight activity is documented in ADOT’s project justification for the widening.

The interchange makes the truck problem worse for a reason that has nothing to do with the truckers. Heavy vehicles need longer stopping distances and more room to change lanes. The geometry at the interchange doesn’t give them that room during peak volumes. A truck in the middle lane of a three-lane merge, trying to make an exit while cars cut across, creates a crash pattern that’s visible in ADOT’s category data.

Ghost-fleet and chameleon-carrier issues on I-10 compound the liability picture after a crash. If the truck that hit you is operating under a questionable MC authority or the insurance is layered through a freight broker, identifying the right defendant becomes a preservation-of-evidence issue.

The Structural Fix

ADOT’s $396M SR-347 Improvement Project adds one lane in each direction across 14 miles from I-10 to the Maricopa city limits, with grade-separated interchanges at Riggs Road and Mammoth Way. The engineering rationale for the fix isn’t controversial. Four lanes divided with proper auxiliary lanes at the interchange would reduce the speed-differential problem, give commercial vehicles room to operate, and add capacity for bicycle and pedestrian facilities on the shoulders.

ADOT awarded the design-build contract to Sundt Construction in early 2026. Pavement rehabilitation started summer 2026. Widening and interchange construction is expected to begin winter 2026-2027, with full completion roughly 3.5 years from start.

The project took more than a decade of local advocacy from Maricopa city officials and regional partners to reach this point. Funding is split: the Pinal County segment (I-10 to Riggs Road) is programmed at $136.3M in FY27, partly through a $50M contribution from the City of Maricopa and Pinal County. The Maricopa County segment (Riggs Road to the city limits) is programmed for FY31 through Proposition 479 and the MAG Freeway Lifecycle program.

What You Can Do

Defensive driving at the interchange is the first line. Leave extra following distance when SR-347 volumes are high. Watch for brake lights two or three cars ahead, not just the car in front of you. Don’t ride the left lane if you’re not passing. Most of all, stay out of truck blind spots on the approach to the interchange.

If you can adjust your commute window, even 15 minutes off peak makes the interchange materially safer. The data supports it.

If you’re hit, the evidence window is short. Traffic camera data, truck ELD records, and witness accounts all fade fast. Call a lawyer within 24 to 48 hours if you’re injured. On commercial vehicle claims specifically, the defendant’s insurance representatives will be on the scene or calling you within hours. Anything you say or sign without counsel can cost you the case.

The Bigger Point

Maricopa is growing faster than its only highway out of town can handle. The interchange is where that gap becomes measurable in crash reports. The $396M fix is now funded and under contract. But construction on the full corridor and the I-10 interchange runs through roughly 2029-2030, which means Maricopa commuters will navigate the current configuration for several more years.

Until the widening is complete, the corridor demands attention from every driver using it.

For the legal and process context, see Ron DeBrigida’s guide to Arizona car crash law, Stephanie Ramirez’s car crash first 48 hours, the car crashes practice overview.

Frequently asked questions

How many commuters use the SR-347 and I-10 interchange daily?
ADOT's SR-347 Improvement Project documentation states SR-347 averages more than 31,000 vehicles per day, with the majority heading to or from the I-10 interchange during morning and evening peaks. ADOT projects that volume to roughly double by 2040, which is part of the project justification for the $396M widening.
What's the most common crash type at the SR-347 and I-10 interchange?
Rear-end crashes during merge-zone queue backups are the most common, followed by sideswipes during lane changes. Serious crashes involving commercial trucks are overrepresented because of the truck mix on both corridors. Fatal single-vehicle run-off-road events happen at the south-side transition where SR-347 geometry changes.
Is ADOT planning to widen SR-347 or improve the I-10 interchange?
ADOT awarded the SR-347 Improvement Project to Sundt Construction in early 2026. The $396M project adds one lane in each direction along 14 miles from I-10 to the Maricopa city limits, with grade-separated interchanges at Riggs Road and Mammoth Way. Pavement rehabilitation started summer 2026; widening and interchange construction is expected to begin winter 2026-2027, with an estimated 3.5-year completion timeline. Funding is split between the Pinal County segment (FY27, $136.3M) and the Maricopa County segment (FY31, via Proposition 479 and MAG Freeway Lifecycle funds).
Are there alternate routes to get from Maricopa to the I-10?
Yes, but they add substantial time. Sunland Gin Road to I-10 adds roughly 20-30 minutes depending on time of day. Casa Grande via SR-387 and I-10 adds 40 minutes or more. Neither alternate has the traffic volume to serve as a real substitute for SR-347.
What should I do if I'm in a crash at the interchange?
Get to a safe position if possible. The shoulder is narrow in the merge zone. Call 911. Note the milepost. Cell coverage is patchy on segments of SR-347. Take photos of the crash scene, vehicle positions, and the lane configuration. Get witness contacts. Don't give a recorded statement to the other driver's insurer. Commercial vehicle crashes have preservation-of-evidence implications, so call a lawyer before any trucking-company representative contacts you.
Who's responsible for safety on SR-347 and at the interchange?
SR-347 is a state route managed by ADOT. The I-10 corridor is federal interstate under ADOT operational authority. Local Maricopa officials advocate for improvements but don't make engineering decisions directly. Claims against ADOT or the state require a Notice of Claim within 180 days under ARS 12-821.01.
How much of a $30K settlement will I get?
A $30,000 Arizona personal injury settlement often gets reduced by attorney fees, case costs, and any medical liens or health plan reimbursement claims, so the net can be much lower than the gross amount. In Arizona, attorney contingency fees are governed by the fee agreement and ethics rules, and medical liens can attach under ARS 33-931 through 33-934, while Medicare, Medicaid, or ERISA health plans can also seek repayment from settlement funds. Personal injury compensation for physical injuries or sickness is generally excluded from federal income tax under IRC § 104(a)(2), but punitive damages and interest can be taxable. The exact amount a person injured receives depends on the fee percentage, litigation costs, and the size of any liens, so two $30,000 settlements can produce very different net payouts.
What is the hardest injury to prove?
In Arizona cases, the hardest injuries to prove are usually those that do not show clearly on imaging and rely on a person’s description of symptoms, such as soft tissue injuries (whiplash, sprains), mild traumatic brain injuries, chronic pain conditions, and psychological trauma. These injuries often involve delayed onset, fluctuating pain, or cognitive and emotional changes that standard X‑rays or CT scans don’t capture, so insurers and defense attorneys may dispute both causation and severity. Arizona law allows people injured to present medical records, expert testimony, pain journals, and witness statements to substantiate these “invisible” harms, and non‑economic damages for pain and suffering are permitted without a statutory cap (see Ariz. Const. art. 2, § 31; art. 18, § 6). ADOT crash data show thousands of injury collisions in Arizona each year, and in 2024 many involved rear‑end and angle crashes where soft tissue and concussion‑type injuries are common, yet often underdocumented.
What not to say to an injury lawyer?
People injured in Arizona cases generally risk harming their claims when they tell a lawyer anything untrue, exaggerated, or incomplete. Common problems include denying prior injuries or prior claims, minimizing symptoms (“I’m fine” or “it’s not that bad”), or hiding gaps in medical care, even though insurers will usually uncover this through records and claims databases. Admitting legal “fault” in strong terms (“It was all my fault”) can also complicate how comparative fault works under A.R.S. § 12‑2505, which lets a jury assign percentages of responsibility. Leaving out things that seem embarrassing, like social media posts, pre‑existing conditions, or statements already given to an adjuster, often causes bigger issues later when defense attorneys obtain that information. Arizona’s rules on attorney‑client privilege (Arizona Rule of Evidence 502) protect confidential talks with your lawyer, so people injured typically benefit from full, accurate disclosure instead of trying to “spin” the facts.
Is it worth hiring an attorney after a car accident?
Arizona law never requires a lawyer after a crash, but data and state rules explain why many people injured decide it is worth it. Arizona uses an at‑fault system, so the driver who caused the crash (and their insurer) is responsible for damages under ARS § 28‑4009, and insurance companies often try to limit payouts. National research from the Insurance Research Council reports that people with attorneys receive settlements several times higher on average than people who handle claims alone, even after contingency fees. An attorney can help apply Arizona’s comparative fault rule (ARS § 12‑2505), document injuries and future losses, and track deadlines, including the typical two‑year limit to file most injury lawsuits (ARS § 12‑542). In very minor crashes with only property damage and no injuries, people sometimes resolve claims directly with insurers, but where there are medical bills, lost income, or disputed fault, representation often has a measurable financial impact.

Sources & references

Sources
  1. Arizona Department of Transportation. (2026). SR 347 Improvement Project. Retrieved June 8, 2026, from https://azdot.gov/sr347
  2. Arizona Department of Transportation. (2026). SR-347 Corridor Widening, I-10 to City of Maricopa. Retrieved June 8, 2026, from https://azdot.gov/projects/central-district-projects/sr-347-corridor-widening-i-10-city-maricopa
  3. Arizona Department of Transportation. (2024). Average Annual Daily Traffic Report 2023, Arizona State Routes. Retrieved from https://azdot.gov/sites/default/files/2024-07/2023-AADT-PUBLICATION_StateRoutes.pdf
  4. Arizona Department of Transportation. (2025). 2024 Arizona Motor Vehicle Crash Facts. Retrieved from https://azdot.gov/sites/default/files/2025-07/2024-Crash-Facts.pdf
  5. Arizona State Legislature. (2025). ARS 12-821.01: Notice of Claim. Retrieved from https://www.azleg.gov/ars/12/00821-01.htm
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