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Lesson 5 of 28 · Section 3: Dangerous Driving

Vision, fatigue, emotions and hot vehicles

Being tired, upset or unable to see well makes you a dangerous driver. New Hampshire gives specific numbers for sleep, breaks and how fatigue compares to alcohol.

Topic
Safe driving
Key points
9
Numbers
5
Manual
Handbook pp. 7 to 10
What you must know

Key points

  1. If you need corrective lenses, always wear them to drive and avoid dark or tinted lenses at night.

    Source: Handbook p. 7
    “Always wear them when driving. Avoid using dark or tinted corrective lenses at night.”
    New Hampshire Driver's Manual, Handbook p. 7

  2. The average person needs 7 to 9 hours of sleep to stay alert.

    Source: Handbook p. 7
    “the average person needs 7 to 9 hours of sleep to maintain proper alertness during the day.”
    New Hampshire Driver's Manual, Handbook p. 7

  3. On long trips, stop at least every 2 hours.

    Source: Handbook p. 7
    “During long trips, plan to stop at least every 2 hours to stretch or get a cup of coffee or soft drink.”
    New Hampshire Driver's Manual, Handbook p. 7

  4. Before you get too tired, pull off for a 15 to 20 minute nap or find a place to sleep.

    Source: Handbook p. 7
    “take a 15 to 20 minute nap or find a place to sleep for the night.”
    New Hampshire Driver's Manual, Handbook p. 7

  5. After 18 hours awake, a driver performs like someone with a BAC of 0.05%.

    Source: Handbook p. 7
    “a driver who is up for a continuous 18 hours will typically exhibit performance levels similar to that of a person with a Blood Alcohol Concentration (BAC) level of 0.05%.”
    New Hampshire Driver's Manual, Handbook p. 7

  6. After 21 and 24 hours without sleep, performance is like a BAC of 0.08% and 0.10%.

    Source: Handbook p. 7
    “After 21 and 24 hours without sleep, performance mimics a BAC of 0.08% and 0.10%, respectively.”
    New Hampshire Driver's Manual, Handbook p. 7

  7. Following too closely, speeding, unsafe lane changes and ignoring signals are signs of aggressive driving.

    Source: Handbook p. 8
    “Some behaviors typically associated with aggressive driving include: speeding, following too closely, unsafe lane changes, improperly signaling, and failing to obey traffic control devices”
    New Hampshire Driver's Manual, Handbook p. 8

  8. If you are upset, take time to calm down before driving; a short walk or nap may help.

    Source: Handbook p. 10
    “A driver should take time to calm down before getting behind the wheel. Taking a short walk or nap prior to getting behind the wheel may help.”
    New Hampshire Driver's Manual, Handbook p. 10

  9. Never leave a child in a vehicle unattended for any length of time.

    Source: Handbook p. 10
    “Never leave a child in a vehicle unattended for any length of time.”
    New Hampshire Driver's Manual, Handbook p. 10
Exact figures

Numbers to know

NumberWhat it meansManual
7 to 9 hourssleep the average person needsHandbook p. 7
2 hoursstop at least this often on long tripsHandbook p. 7
15 to 20 minuteslength of a rest stop napHandbook p. 7
18 hours = 0.05%fatigue compared to BACHandbook p. 7
21 and 24 hours = 0.08% and 0.10%fatigue compared to BACHandbook p. 7
Check yourself

3 questions from the New Hampshire practice test

  1. 1. On a long trip, how often does the New Hampshire manual say to plan a stop to fight fatigue?

    1. Every 30 minutes
    2. At least every 2 hours
    3. Every 4 hours
    4. Only when you feel sleepy
    Show answer

    At least every 2 hours. The fatigue advice is specific: during long trips, plan to stop at least every 2 hours to stretch or get a cup of coffee or a soft drink. Waiting until you feel sleepy is exactly what the manual warns against, because fatigue slows decisions before you notice it. The other tools are getting 7 to 9 hours of sleep, taking a 15 to 20 minute nap at the next exit or rest area before you get too tired, avoiding late night driving, and sharing the driving with a companion.

  2. 2. According to the New Hampshire manual, a driver who has been awake for 18 hours performs like a driver with what BAC?

    1. About 0.05%
    2. About 0.08%
    3. About 0.02%
    4. About 0.10%
    Show answer

    About 0.05%. The manual compares drowsy driving to drunk driving with three data points. A driver who has been up for a continuous 18 hours typically performs like a person with a blood alcohol concentration of 0.05%. After 21 hours without sleep performance mimics 0.08%, and after 24 hours it mimics 0.10%. The higher figures are the wrong answers for the 18 hour mark. Unlike alcohol, there is no breathalyzer for sleep, so the choice not to drive tired rests on the driver.

  3. 3. How long does the New Hampshire manual say a child may be left unattended in a vehicle?

    1. Never, for any length of time
    2. Up to 10 minutes with a window open
    3. Up to 5 minutes in cool weather
    4. As long as the engine and air conditioning are running
    Show answer

    Never, for any length of time. In warm weather a vehicle begins to heat up immediately after it is turned off, and it takes only minutes to reach dangerous temperatures. The manual passes on the National Highway Traffic Safety Administration advice never to leave a child in a vehicle unattended for any length of time. An open window or cool day does not create a safe interval. Check the whole vehicle, especially the back seat, before locking it, and keep keys and fobs out of children's reach.

Next step

Practice this topic

Lock it in with safe driving questions from the free New Hampshire practice test. Every answer comes with a plain English explanation.

Practice this topicAll 28 lessons

Source: the New Hampshire Driver's Manual, Section 3: Dangerous Driving. This lesson is a plain English summary, not the law itself; where it differs, the manual and the statute govern. Last checked 2026-09-27.

Reviewed by , CA DOI #4037122 · Last updated 2026-09-27