Idaho posts 80 mph on studied rural sections of I-84, I-86 and I-15, with 75 mph on other interstate mileage, up to 70 mph on state highways, and a 35 mph default in urban districts.
Idaho speed limits at a glance
| Road type | Limit |
|---|---|
| Cities, towns, business districts | 35 mph (56 kph) |
| Residential / school zones | 35 mph (56 kph) |
| Rural highways | 70 mph (113 kph) |
| Interstates / freeways | 80 mph (129 kph) |
About speed limits in Idaho
Idaho's interstates carry a base limit of 75 mph, and since July 2014 the state has been allowed to raise approved sections to 80 mph after an engineering and traffic study. The Idaho Transportation Department has posted 80 mph across long rural stretches of I-84, I-86 and I-15 in southern Idaho, while segments through the Boise metro area and other cities run lower. Trucks are capped at 70 mph on the 80 mph sections. Non-interstate state highways top out at 70 mph where studies support it, with 65 mph common on two-lane routes.
Idaho pairs its numeric limits with a basic rule: you must always drive at a speed that is reasonable and prudent for conditions, so you can be cited below the posted number in fog, snow or heavy traffic. The 2014 move to 80 mph made Idaho one of the first states after Utah, Wyoming and Texas to break the 75 mph ceiling, and the differential truck limit is a distinctive feature drivers notice on the Snake River Plain corridors.
Unusually for the region, Idaho's default in any residential, business or urban district is 35 mph rather than 25, unless a different limit is posted. In practice cities such as Boise sign most neighborhood streets at 25 mph, and school zones drop to 20 mph during posted hours, so watch signs closely because the statutory default is higher than what is usually posted.
Idaho law prohibits automated traffic enforcement, so no speed cameras or red-light cameras operate in the state. Enforcement rests with Idaho State Police and local agencies, and legislative attention in recent years has focused on fine schedules and work-zone safety rather than camera programs.
Enforcement
Idaho State Police patrol the interstates with radar and unmarked units, concentrating on the I-84 corridor and construction zones. Automated camera enforcement is prohibited by state law, so all citations come from live stops.
Tolerance
There is no statutory grace margin, and Idaho's fine schedule starts at just 1 mph over. In practice troopers on 80 mph rural interstates prioritize clearly excessive or condition-inappropriate speed over marginal overages.
Speeding fines in Idaho
Idaho uses a simple fixed schedule: roughly 90 dollars total for 1-15 mph over and about 155 dollars for 16 or more over, with higher amounts in school and construction zones. Fines are the same statewide rather than set per court, and excessive speed can also be charged as reckless driving.
Frequently asked questions
What is the maximum speed limit in Idaho?
80 mph on interstate sections approved after an engineering study, mainly rural stretches of I-84, I-86 and I-15. Other interstate mileage is 75 mph, and trucks are limited to 70 mph on the 80 mph sections.
When did Idaho get 80 mph speed limits?
A 2014 law authorized raising interstate limits from 75 to 80 mph where studies showed it was safe, and the first 80 mph signs went up in July 2014. Idaho was among the earliest states outside Texas and Utah to adopt 80 mph.
What is the residential speed limit in Idaho?
The statutory default in residential, business and urban districts is 35 mph unless otherwise posted, which is higher than most states. Cities typically post 25 mph on neighborhood streets and 20 mph in school zones, and posted signs control.
Does Idaho use speed cameras?
No. Idaho bans automated speed enforcement by statute, so there are no speed or red-light cameras. Tickets are issued only by officers during traffic stops.
Speed limits in nearby states
- Washington speed limit — interstate, rural highway, and city limits.
- Oregon speed limit — interstate, rural highway, and city limits.
- Utah speed limit — interstate, rural highway, and city limits.
- Montana speed limit — interstate, rural highway, and city limits.
- Nevada speed limit — interstate, rural highway, and city limits.
Related tools
- Convert MPH to KPH — convert any speed reading between units.
- Car speed test — verify your speedometer accuracy.
- Live GPS speedometer — see your actual speed in the browser.
- Stopping distance calculator — how far you need to brake from each speed.
- US speed limits overview — federal background and national patterns.