Iowa speed limits and key traffic laws

By the end of this topic you can

• You can state Iowa's default limits for business, residence, school and suburban districts.
• You can explain the interstate maximum and minimum speeds.
• You can describe what to do when you meet or follow a stopped school bus.
• You can apply the Move Over or Slow Down law.
• You can explain why work zone fines are higher.

What you need to know and understand

• Unless signs say otherwise: 20 mph in business districts, 25 mph in residence or school districts and 45 mph in suburban districts.
• Rural interstates are generally 70 mph, and the minimum on the interstate is 40 mph.
• Speed limits are maximums for ideal conditions; you must slow down for rain, snow, fog or traffic.
• Scheduled fines for moving violations are doubled in road work zones.
• When meeting a school bus with flashing amber lights, slow to 20 mph or less and be ready to stop.
• Stop no closer than 15 feet behind a school bus with its stop arm out.

Iowa's default speed limits

On other rural highways and county roads, follow the posted signs, and remember that unpaved gravel roads have lower night-time limits than daytime limits. When in doubt, choose the lower speed.

• Business district: 20 mph.
• Residence or school district: 25 mph.
• Suburban district: 45 mph.
• Fully controlled-access, divided, multilane highways: 65 mph, unless posted lower.
• Interstate highways: 70 mph, unless posted lower (urban interstate stretches are often lower).
• Interstate minimum: vehicles that cannot keep up 40 mph are not allowed on the interstate.

Stopped school buses

School buses turn on flashing amber lights before stopping, then red lights and a stop arm. If you are behind the bus, do not pass while red or amber lights flash, and stop at least 15 feet back when the stop arm is out. Stay stopped until the arm is retracted and the bus moves.

If you are coming toward the bus, slow to no more than 20 mph when the amber lights flash and stop when the stop arm comes out. The only exception is on a road with two or more lanes in each direction, where oncoming traffic does not have to stop. A first offense carries a fine of $345 to $930 and can lead to a license suspension of up to 180 days or a driver improvement program.

Move over, work zones and other Iowa rules

Our deeper guide to the Iowa school license and our permit practice test cover more of these rules.

• Move Over or Slow Down: when you approach a stopped emergency, tow, maintenance, construction, garbage or recycling vehicle with flashing lights, or any stopped vehicle with hazard lights on, change to a lane not next to it. If you cannot do that safely, slow below the posted limit and be ready to stop.
• Work zones: obey flaggers and changing speed limits; scheduled fines double, and speeding fines in work zones range from $195 up to $1,285.
• Headlights: required from sunset to sunrise and whenever you cannot see 500 feet ahead.
• Steer It, Clear It: after a crash with no injuries, move a drivable vehicle out of the traffic lanes.

Common mistakes

• Treating 70 mph as a target on every interstate. Many urban stretches are posted lower, and conditions may call for less.
• Passing a bus with amber lights flashing because the stop arm is not out yet. Amber means prepare to stop.
• Staying in the lane next to a stopped tow truck. The law covers tow, maintenance and garbage trucks too, not just police.

Test yourself: Iowa speed limits and key traffic laws

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

Go deeper

• Iowa School License
• Iowa Permit Practice Test
• Iowa Permit Test