A driver is travelling along a motorway when they notice a hazard ahead. Explain how the driver's thinking distance and braking distance each contribute to the total stopping distance, and describe TWO factors that could increase the thinking distance.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Road safety researchers studying motorway accidents found that many collisions occurred because drivers did not stop in time after spotting a hazard. They noted that stopping distance has two distinct components, each affected by different factors.
Model answer (4 marks)
Thinking distance is the distance the car travels while the driver is reacting to the hazard – that is, during the reaction time before the brakes are applied. Braking distance is the distance travelled after the brakes are applied until the vehicle comes to a stop. Two factors that can increase the thinking distance are tiredness (which slows the driver’s reaction time) and higher speed (which lengthens the distance covered during the same reaction time).
Examiner tips
- Use the exact terms ‘thinking distance’ and ‘braking distance’.
- Show the relationship: reaction time × speed = thinking distance.
- Mention two distinct factors, e.g. tiredness and higher speed.
Common mistakes
- Confusing thinking distance with braking distance; writing them as the same thing.
- Listing only one factor or repeating the same factor twice.
- Using vague terms like ‘slow’ instead of specific causes such as tiredness or higher speed.
Mark scheme (4 marks)
- Thinking distance is the distance travelled during the driver's reaction time (before the brakes are applied)
- Braking distance is the distance travelled under the braking force (after the brakes are applied) until the vehicle stops
- One valid factor that increases thinking distance, e.g. tiredness / distractions / influence of drugs or alcohol / higher speed
- A second, different valid factor that increases thinking distance
Key terms in this question
stopping distance · thinking distance · braking distance
Related
- All OCR GCSE Physics A: Gateway Science (J249) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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