Idaho speed limits and key traffic laws

By the end of this topic you can

• You can state Idaho's default speed limits for different roads.
• You can apply the basic speed rule in bad conditions.
• You can explain when you must stop for a school bus.
• You can describe what to do when passing a stopped emergency vehicle.

What you need to know and understand

• Interstates: 75 mph unless posted otherwise, and up to 80 mph where posted.
• State highways: 65 mph unless posted otherwise, and up to 70 mph where posted.
• Residential, business and urban districts: 35 mph unless posted otherwise.
• Driving too slowly and blocking traffic also breaks the basic rule, and you may not hold up traffic in the far left lane.
• School zone and work zone limits must be obeyed, and work zone speeding can bring an enhanced fixed penalty.
• Racing or speed contests on any public road are illegal.

The passing speed exception

Idaho has an unusual rule for two-lane roads. If you drive a car, pickup or motorcycle that is not towing, and you are passing a vehicle going below the limit on a two-lane road posted at 55 mph or more, you may go up to 15 mph over the posted limit while passing. You must return to your lane and drop back to the limit as soon as practical. The exception never applies in work zones.

School buses

When a school bus shows flashing red lights or extends its stop arm, traffic must stop and stay stopped until the lights stop flashing and all children are clear of the road and the bus. Passing is also prohibited while a school bus is stopped to load or unload.

• Same direction as the bus: always stop.
• Two-lane road, either direction: stop.
• Opposite direction on a highway with four or more lanes, two each way: you do not have to stop, but slow down and watch for children.

Moving over for stopped vehicles

When you approach a stopped emergency or police vehicle with lights flashing, or a stopped tow truck or incident response vehicle, slow to below the posted limit and go carefully. On a road with two or more lanes in your direction, also move into a lane that is not next to the stopped vehicle as soon as it is safe.

If an emergency vehicle comes up behind you with a siren or flashing red or blue lights, pull to the right edge of the road, clear of any intersection, and stop until it has passed.

Common mistakes

• Treating the posted limit as a safe speed in snow, rain or smoke. The basic rule still applies.
• Using the passing exception in a work zone, on a road posted below 55 mph or while towing.
• Passing a school bus on a two-lane road because you are going the other way.
• Staying in the left lane of a multi-lane road while slower than the traffic around you.

Test yourself: Idaho speed limits and key traffic laws

Answer each question, then read the explanation. Questions come in a random order each time.

Go deeper

• Idaho GDL Rules and the Supervised Instruction Permit
• Idaho Permit Test
• Idaho Parent-Led Driver Training