I-17 Trucking Guide: Phoenix to Flagstaff Elevation, Grades & Safety Tips

The Elevation Profile

I-17 is a 146-mile corridor that transforms from Sonoran desert to mountain pine forest. The elevation change is dramatic:

That is 5,800+ feet of elevation gain in 146 miles. The grades are real, the runaway ramps are there for a reason, and Flagstaff weather is completely different from Phoenix weather two hours south.

Dangerous Segments

Black Canyon Descent (Southbound MP 251-244)

Steep sustained grade descending into Black Canyon City. Runaway truck ramps are available on the right. This section kills truckers who do not downshift before the grade begins. Check your brakes before the descent.

Camp Verde Valley

Steep descent from BOTH directions into the Camp Verde valley. Runaway truck ramps on both hills. The dual-direction grade catches drivers who think the danger is only one way.

6% Grade Warning (26 Miles South of I-40)

Signs warn of a 6% grade approximately 26 miles south of the I-40 junction. This is the final steep section before reaching Flagstaff elevation. Gear down.

Flagstaff: A Different World

Flagstaff sits at 7,000 feet. In summer, Phoenix is 115 degrees while Flagstaff is 80. In winter, Phoenix is 65 and sunny while Flagstaff has snow, ice, and chain requirements.

• Winter chain/traction requirements are posted when conditions warrant in the Flagstaff area
• If you leave Phoenix in a t-shirt, you may arrive in Flagstaff in a blizzard
• Check az511.gov for current Flagstaff conditions before departure

Insurance Implications

I-17 grade accidents generate high-severity claims. A runaway truck on the Black Canyon descent or Camp Verde grades causes catastrophic damage. The corridor is a factor in Arizona insurance risk assessment. We recommend $1M CSL minimum. Call RMS at (208) 800-0640.