AQA · GCSE · Combined Science

    Course version: 8464 · Version from Sept 2018

    A driver’s reaction time can be affected by tiredness, drugs and alcohol.…

    Full specification wording

    Reaction time: A driver’s reaction time can be affected by tiredness, drugs and alcohol. Distractions may also affect a driver’s ability to react.

    A driver’s reaction time is not fixed; it depends on the driver’s state and surroundings.

    Checked against the AQA 8464 specification (opens in a new tab) on .

    • Point 2 of 5
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    A driver’s reaction time is not fixed; it depends on the driver’s state and surroundings. Tiredness slows nerve processing and decision making, so the interval between seeing a hazard and braking increases. Drugs and alcohol can slow brain activity, impair judgement and reduce coordination, again lengthening reaction time. Distractions such as a ringing phone, loud passengers or looking at a satnav compete for attention, so the hazard may be detected later or the response may be delayed. Because thinking distance equals speed multiplied by reaction time, any increase in reaction time increases the distance travelled before braking begins, raising the risk of a collision.

    What earns the marks

    • Tiredness slows the driver’s processing of information and increases reaction time.
    • Drugs and alcohol impair brain function, judgement and coordination, which increases reaction time.
    • Distractions divide the driver’s attention, so a hazard may be detected later or the response may be delayed.
    • An increased reaction time increases thinking distance because thinking distance = speed × reaction time.
    • A longer thinking distance at a given speed means the vehicle travels further before braking, increasing collision risk.
    • Reaction time is affected by both the driver’s physiological state and external distractions, so it is not a fixed value.

    Common mistakes and how to put them right

    • Thinking alcohol only affects judgement and not reaction time.

      Put it right: Link alcohol to a longer interval between stimulus and response.

    • Assuming distractions change braking distance.

      Put it right: Separate thinking distance from braking distance.

    • Treating tiredness as harmless because the driver is still awake.

      Put it right: Explain that tiredness increases reaction time.

    Exam tips

    • Link each factor to the effect on reaction time and then to the effect on thinking distance, using thinking distance = speed × reaction time.
    • Use comparative language such as increases, lengthens or delays rather than vague words such as affects.
    • When describing distractions, name a specific example such as using a phone or talking to a passenger, and state how it delays the response.

    Try the lesson

    The start of the Reaction time: A driver’s reaction time can be affected by tiredness, drugs and alcohol. Distractions may also affect a driver’s ability to react. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Which of these is a distraction that may increase a driver’s reaction time?

    Listen

    A driver’s reaction time is not fixed; it depends on the driver’s state and surroundings. Tiredness slows nerve processing and decision making, so the interval between seeing a hazard and braking increases. Drugs and alcohol can slow brain activity, impair judgement and reduce coordination, again lengthening reaction time. Distractions such as a ringing phone, loud passengers or looking at a satnav compete for attention, so the hazard may be detected later or the response may be delayed. Because thinking distance equals speed multiplied by reaction time, any increase in reaction time increases the distance travelled before braking begins, raising the risk of a collision. A strong answer earns marks for these points. Tiredness slows the driver’s processing of information and increases reaction time. Drugs and alcohol impair brain function, judgement and coordination, which increases reaction time. Distractions divide the driver’s attention, so a hazard may be detected later or the response may be delayed. An increased reaction time increases thinking distance because thinking distance = speed × reaction time. A common slip: Thinking alcohol only affects judgement and not reaction time: alcohol also slows reactions and coordination. Instead, link alcohol to a longer interval between stimulus and response. Exam tip: Link each factor to the effect on reaction time and then to the effect on thinking distance, using thinking distance = speed × reaction time.

    See it

    A top-down flowchart. Three starting boxes sit at the top: Tiredness, Drugs and alcohol, and Distractions. Tiredness leads to a box reading slows nerve processing and decision making. Drugs and alcohol leads to a box reading slow brain activity, impair judgement and reduce coordination. Distractions leads to a box reading hazard detected later or response delayed. All three of these boxes lead into a single box reading increased reaction time. That box leads to a box reading longer thinking distance (thinking distance = speed × reaction time), which leads to a box reading vehicle travels further before braking, which finally leads to a box reading greater risk of collision.
    It shows how tiredness, drugs and alcohol, and distractions increase reaction time, which lengthens thinking distance and raises collision risk.

    Key words

    Say what each word means before you turn the card.

    Reaction time

    Try answering aloud or in your head before turning the card.

    Tiredness

    Try answering aloud or in your head before turning the card.

    Drugs and alcohol

    Try answering aloud or in your head before turning the card.

    Distractions

    Try answering aloud or in your head before turning the card.

    See every definition
    Reaction time
    The interval between seeing a hazard and braking, which is not fixed and depends on the driver's state and surroundings.
    Tiredness
    Slows nerve processing and decision making, so the interval between seeing a hazard and braking increases.
    Drugs and alcohol
    Can slow brain activity, impair judgement and reduce coordination, again lengthening reaction time.
    Distractions
    Things such as a ringing phone, loud passengers or looking at a satnav compete for attention, so a hazard may be detected later or the response delayed.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. Three starting boxes sit at the top: Tiredness, Drugs and alcohol, and Distractions. Tiredness leads to a box reading slows nerve processing and decision making. Drugs and alcohol leads to a box reading slow brain activity, impair judgement and reduce coordination. Distractions leads to a box reading hazard detected later or response delayed. All three of these boxes lead into a single box reading increased reaction time. That box leads to a box reading longer thinking distance (thinking distance = speed × reaction time), which leads to a box reading vehicle travels further before braking, which finally leads to a box reading greater risk of collision.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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