Overview
This lecture explains stopping distance for vehicles, breaks down its two components (thinking distance and braking distance), and examines the factors affecting each, especially the impact of speed.
Stopping Distance Basics
- Stopping distance is the minimum distance a vehicle needs to stop in an emergency.
- Total stopping distance = thinking distance + braking distance.
Thinking Distance
- Thinking distance is how far a car travels during the driver's reaction time.
- Reaction time is the interval between spotting a hazard and applying the brakes.
- Thinking distance increases with higher speed and longer reaction time.
- Poor alertness (tiredness, alcohol, drugs, distractions) increases reaction time and thus thinking distance.
Braking Distance
- Braking distance is the distance traveled from the point brakes are applied to when the car stops.
- Higher speed and greater vehicle mass increase braking distance due to more kinetic energy.
- Worn or faulty brakes increase braking distance by reducing stopping force.
- Poor road conditions (wet or icy) and worn tires decrease friction, increasing braking distance.
Effect of Speed on Stopping Distance
- Thinking distance increases proportionally with speed.
- Braking distance increases with the square of the speed (doubling speed quadruples braking distance).
- Total stopping distance increases more steeply at higher speeds, following a non-linear curve.
Key Terms & Definitions
- Stopping Distance — Total minimum distance needed to stop a moving vehicle in an emergency.
- Thinking Distance — Distance traveled during the driver’s reaction time.
- Braking Distance — Distance covered from brake application to a complete stop.
- Reaction Time — Time between seeing a hazard and starting to brake.
- Traction — The friction between the tires and the road surface.
Action Items / Next Steps
- Review the factors affecting stopping distance and practice interpreting diagrams showing thinking and braking distances.
- Be prepared to answer questions on how speed affects braking and overall stopping distance.