MileCheckArizona's highways run through some of the most extreme driving conditions in the country — hundred-mile desert stretches, monsoon dust storms, and a two-mile elevation swing from Phoenix to Flagstaff. All of it runs on mile markers. Here's how they work across the state, where they matter most, and how to see your exact one plus live AZ511 conditions in real time.
How Arizona numbers its highways
Arizona's mileposts count up from where a route enters the state on its west or south side — I-10 starts near the California line and crosses into New Mexico around mile 391. But Arizona also has two of the strangest numbering quirks in America. I-17's mileposts start at 194 in Phoenix, not zero, because they carry over from the older highway it replaced — so there is no I-17 milepost 1. And I-19 from Tucson to Nogales is posted in kilometers, the only metric interstate in the country. Quirks like these are exactly why MileCheck reads the real roadside data instead of guessing. Mile marker data for every Arizona highway is bundled into the app and works offline.
The corridors people actually drive
- I-10 crosses the state for about 391 miles — California line, Phoenix, Tucson, then out to New Mexico.
- I-40 runs the old Route 66 corridor through Kingman, Williams, and Flagstaff, about 359 miles.
- I-17 climbs from Phoenix at 1,100 feet to Flagstaff at 7,000 — mileposts 194 to 341.
- I-8 heads for San Diego out of Casa Grande through Yuma; US-93 is the Vegas run northwest of Wickenburg; US-60 and SR-87 carry cabin traffic into the high country; the Loop 101, 202, and 303 freeways ring Phoenix.
Where mile markers matter most: dust and elevation
The stretch of I-10 between Phoenix and Tucson around Picacho Peak — roughly mileposts 211 to 219 — is one of the most dangerous dust-storm corridors in the country. When a wall of dust rolls across the interstate, visibility can go from clear to zero in seconds, and ADOT's guidance is to pull completely off, lights out, foot off the brake. Knowing your milepost is how you tell dispatch, your fleet, or the person coming behind you exactly where the wall is. On the other end of the state, I-17's long grades and Flagstaff's seven-thousand-foot winters close roads the desert never has to think about.
Monsoon, dust, and mountain snow
Arizona's closures come in two seasons. From mid-June through September, monsoon storms push haboobs — mile-high walls of dust — across I-10 and I-8, and flash floods can take out desert highways in minutes. In winter, the high country gets serious snow: Flagstaff is one of the snowiest cities in America, and I-40, I-17, and SR-87 all see winter closures and icy-grade restrictions the valley never hears about. Every one of these events is announced by milepost, so getting the live AZ511 alert before you're inside the dust or on the grade is the whole game.
Live AZ511 alerts, in one place
MileCheck pulls live road alerts straight from ADOT's AZ511 system: closures, crashes, construction, and weather hazards, tied to the mile marker and direction. It also reads ADOT's roadside weather stations — surface grip, temperature, and wind — so an icy bridge deck on I-40 or a wind warning near Picacho shows up as an alert, not a surprise.
Everyday and emergency
Whether you're crossing the desert on I-10 where towns are sixty miles apart, timing the I-17 climb on a snow day, or reporting a breakdown where the signal drops, the mile marker is the location Arizona's roads run on. MileCheck shows yours in real time, down to a tenth of a mile, even with no cell service.
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Nearby state guides: California · Nevada · New Mexico · Utah
Essentials: What to tell 911 on the highway · How to find your mile marker · Browse the live mile marker map · All 50 states