Linear Proportionality: Thinking distance is directly proportional to the vehicle's speed. If the speed of the vehicle doubles, the thinking distance also doubles, assuming the reaction time remains constant.
The Kinematic Equation: The relationship is expressed as , where is the velocity in meters per second and is the reaction time in seconds.
Constant Velocity Assumption: During the 'thinking' phase, the vehicle is assumed to be traveling at a constant velocity because the deceleration process has not yet begun.
| Factor | Affects Thinking Distance? | Affects Braking Distance? |
|---|---|---|
| Vehicle Speed | Yes (Linear) | Yes (Squared) |
| Driver Tiredness | Yes | No |
| Icy/Wet Roads | No | Yes |
| Worn Brakes | No | Yes |
| Alcohol/Drugs | Yes | No |
Unit Conversion: Always ensure speed is in and time is in before calculating distance in meters. A common trap is providing speed in .
Proportionality Checks: If a question asks how thinking distance changes when speed triples, the answer is always that it triples (). Do not confuse this with braking distance, which would increase by .
Identifying Factors: When asked to list factors, categorize them into 'Driver factors' (Thinking) and 'Vehicle/Road factors' (Braking) to avoid losing marks for irrelevant information.