I-15 road conditions today

Interstate 15 is the main north-south freight route of the Mountain West, running 1,433 miles from San Diego, California to Sweet Grass, Montana on the Canadian border. It is the longest north-south interstate west of the Rockies, and from Las Vegas north to the Canadian border it is part of CANAMEX, a federal high priority corridor between Mexico and Canada (FHWA). The route ties Southern California's logistics hubs to Las Vegas, Salt Lake City, and the agricultural and energy economies of Idaho and Montana.

The geography is dramatic. From the San Diego coast, I-15 climbs through the Cajon Pass (4,190 ft), the gateway between the LA Basin and the Mojave Desert, then descends to Las Vegas, climbs again across the Virgin River Gorge in Arizona's narrow corner, and continues over high desert to Salt Lake City. North of Salt Lake it threads the Wasatch Front, climbs Monida Pass (6,870 ft) on the Idaho-Montana border, and rolls across high Montana plains to the international crossing at Sweet Grass.

I-15 is one of the highest-volume freight corridors in the West, especially the segment between Barstow and Las Vegas, which carries a continuous stream of containers and produce trucks. Holiday weekends produce notorious traffic jams between Las Vegas and the LA Basin, backups of 20+ miles are routine on Sunday evenings. Winter chain controls are common in the Cajon, Virgin River Gorge, and Monida Pass segments.

• Longest north-south interstate west of the Rocky Mountains
• Part of the CANAMEX high priority corridor from Las Vegas north to the Canadian border (FHWA). The stretch from San Diego to Las Vegas is not
• Crosses six states: CA, NV, AZ (29 miles only), UT, ID, MT
• Cajon Pass (4,190 ft) is the primary truck route between LA and the Mojave
• Virgin River Gorge in AZ is one of the most expensive interstate sections ever built (per mile)
• Monida Pass (6,870 ft) on the ID/MT border is closed regularly in winter
• Carries the bulk of LA→Las Vegas freight and weekend recreational traffic

The passes on or next to Interstate 15 with a full guide: grade, chain-control season, closures and hazards. Next to each is what its own page shows right now, with the agency the reading comes from where there is one.

• Cajon Pass, California, 4,260 ft: No live data
• Monida Pass, Montana / Idaho, 6,823 ft: Surface reading (Idaho 511)
• Halloran Summit, California, 4,610 ft: No chain control (Caltrans)
• Mountain Pass, California, 4,730 ft: No live data
• Cove Fort Summit, Utah, 6,000 ft: No live data
• Malad Summit, Idaho, 4,460 ft: Surface reading (Idaho 511)

Chain rules for the states these passes are in, and for every state on the route that has a chain law:

• California chain law
• Nevada chain law
• Utah chain law
• Idaho chain law
• Montana chain law

National Weather Service alerts in force in the states Interstate 15 runs through. Each one covers a county or a forecast zone, which may be far from the Interstate.

• 8 alerts in California: Air Quality Alert, Coastal Flood Advisory, Wind Advisory, Winter Storm Watch
• 1 alert in Nevada: Winter Storm Watch
• 2 alerts in Arizona: Flood Warning
• 1 alert in Montana: Special Weather Statement