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Iowa driving lesson · Speed, Stopping & Following Distance

Speed limits

A 2-minute lesson from the Iowa course. Read the rules and examples, follow the handbook page references, and check your understanding before you move on.

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Read time
2 minutes
Course unit
Speed, Stopping & Following Distance
Checkpoint questions
6
Source pages
42

The posted speed limit is the MAXIMUM legal speed under ideal driving conditions. Your speed should fit the posted limit, the road conditions, and the weather. When no limit is posted, Iowa sets general limits by type of area and road.

When no speed limit is posted

When no speed limit is posted
WhereLimit
Any business district25 mph
Residential or school district25 mph
Any suburban district45 mph
Any vehicle pulling another vehicle45 mph
Unsurfaced secondary roads, sunset to sunrise50 mph
All trucks on secondary roads, any time of day50 mph
Primary, urban interstate, secondary roads (day)55 mph
Rural interstate highways70 mph
Handbook p. 42 ↗

Know the rule

The 55 mph limit covers all primary roads, urban interstate highways, and secondary roads—including unpaved roads from sunrise to sunset.

Handbook p. 42 ↗

Know the rule

A lower limit may be set for any of these conditions.

Handbook p. 42 ↗
40 mph

Minimum speed on the interstate system

Handbook p. 42 ↗

Know the rule

Vehicles that cannot go at least 40 mph under normal conditions are not allowed on the interstate.

Handbook p. 42 ↗

Know the rule

Driving too fast is a major cause of crashes, but driving too slow can also cause a crash. Try to drive with the general flow of traffic.

Handbook p. 42 ↗

Know the rule

The faster you go, the more distance it takes to turn, slow, or stop.

Handbook p. 42 ↗

Put it into practice

It's 9 p.m. on an unpaved county road with no posted limit. The general limit is 50 mph after sunset—and slower still if dust, gravel, or darkness call for it.

Check your understanding

Read the question, decide on an answer, then open it to check the explanation. These are Roadwise study questions based on the source handbook.

If no speed limit is posted, what is the general limit in a residential district?
  1. 35 mph
  2. 45 mph
  3. 25 mph
  4. 55 mph

Answer: 25 mph

The unposted limit in a residential or school district is 25 mph.

Handbook p. 42 ↗
What is the unposted speed limit on rural interstate highways?
  1. 55 mph
  2. 65 mph
  3. 60 mph
  4. 70 mph

Answer: 70 mph

The general unposted limit on rural interstate highways is 70 mph.

Handbook p. 42 ↗
What is the minimum speed allowed on the Iowa interstate system?
  1. 40 mph
  2. 25 mph
  3. 55 mph
  4. 30 mph

Answer: 40 mph

The interstate system has a minimum speed of 40 mph; vehicles that can't reach it aren't allowed on the interstate.

Handbook p. 42 ↗
On an unsurfaced secondary road during the day, what is the general speed limit?
  1. 50 mph
  2. 55 mph
  3. 45 mph
  4. 70 mph

Answer: 55 mph

Unsurfaced secondary roads carry a 55 mph limit from sunrise to sunset.

Handbook p. 42 ↗
What is the unposted nighttime limit for trucks on unsurfaced secondary roads?
  1. 55 mph
  2. 40 mph
  3. 50 mph
  4. 70 mph

Answer: 50 mph

Unsurfaced secondary roads carry a 50 mph limit at night, and for all trucks at any time.

Handbook p. 42 ↗
A vehicle towing another vehicle has a general unposted limit of 55 mph in Iowa.
  1. True
  2. False

Answer: False

False. The manual lists 45 mph as the general limit for any vehicle pulling another vehicle.

Handbook p. 42 ↗
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