State comparison · Updated October 2026
Idaho vs. Utah Driving Laws (2026)
Idaho and Utah part ways on 8 of 9 topics we track: phone law, learner's permit age, car insurance, car sales tax, car inspection, new resident deadline, helmet law and lane splitting.
On a trip from Boise to Salt Lake City crosses the state line, and 8 of the nine rules change on the way. Main routes are I-84 on the Idaho side and I-15 on the side of Utah; the capitals, Boise and Salt Lake City, write the laws for their side.
The biggest gap: mandatory liability limits differ: 25/50/15 versus 30/65/25. People who live in Meridian who travel to West Valley City, or the other way around, deal with both sets of laws: Idaho's on I-15 and Utah's once they cross on I-80. Read the Idaho vs Utah guide when moving from Boise to Salt Lake City.
For a quick visit from Boise to Salt Lake City, keep a helmet and proof of insurance, plan the route ahead of time, and watch for the same 80 mph top limit at the border.
| Topic | Idaho | Utah |
|---|---|---|
| Max speed limit | 80 mph | 80 mph |
| Phone law | Hands-free law | Texting ban only |
| Learner's permit age | Permit at 14 | Permit at 15 |
| Car insurance | 25/50/15 | 30/65/25 |
| Car sales tax | 6% | 4.85% |
| Car inspection | No regular inspection | Emissions only |
| New resident deadline | 30 days | Right away |
| Helmet law | Under 18 | Under 21 |
| Lane splitting | Not allowed | Filtering only |
Driving laws side by side: Idaho vs Utah
Idaho vs Utah: Idaho and Utah match on 80 mph for max speed limit.
Cell phone and texting laws: Idaho vs Utah
Idaho is stricter on phone law, with Idaho with hands-free law and Utah at texting ban only. A call that is legal in Boise may not be in Salt Lake City on the other side.
Learner's permit age: Idaho vs Utah
Utah is later on learner's permit age, with Idaho at permit at 14 and Utah with permit at 15. A new driver from Boise taking a trip to Salt Lake City are bound by Utah's provisional limits while in the state.
Owning a car side by side: Idaho vs Utah
Car insurance: Idaho vs Utah
The law is higher in Utah on car insurance: Idaho at 25/50/15 and Utah at 30/65/25. Idaho is at-fault and Utah is no-fault. A policy written in Boise must be updated if you relocate to Salt Lake City.
Car sales tax: Idaho vs Utah
Utah is lower on car sales tax, with Idaho with 6% and Utah with 4.85%. For a $30,000 purchase, state tax comes to roughly $1,800 in Idaho and $1,455 in Utah. Buyers from Meridian and West Valley City pay the tax of their home state, not the dealer's.
Car inspection: Idaho vs Utah
Idaho is lighter on car inspection, with Idaho at no regular inspection and Utah with emissions only. Owners in Meridian is inspected under Idaho rules, even if it frequently goes to West Valley City.
New resident deadlines: Idaho vs Utah
Idaho is longer on new resident deadline: Idaho at 30 days and Utah with right away. Households relocating from Meridian to West Valley City should book DMV visits ahead.
Motorcycle compared: Idaho vs Utah
Helmet law: Idaho vs Utah
Utah is stricter on helmet law: Idaho with under 18 and Utah at under 21. Riders heading from Boise toward Salt Lake City must follow Utah's helmet rule on arrival.
Lane splitting laws: Idaho vs Utah
Idaho is stricter on lane splitting: Idaho at not allowed and Utah at filtering only. Commuters riding between Meridian and West Valley City must change habits at the line.
Moving or buying across the border
- Idaho vs Utah: moving from Idaho to Utah means 60 days for the car registration and right away, as soon as you become a resident for a license.
- The other way: 30 days for registration and 30 days to switch licenses.
Idaho vs Utah: questions
Which has the higher speed limit, Idaho or Utah?
Both Idaho and Utah top out at 80 mph.
Where is the car tax smaller, Idaho or Utah?
Utah charges less at the state level (6% vs. 4.85%).
Do I need a helmet in both Idaho and Utah?
Idaho: Under 18; Utah: Under 21.