Stopping Distance
Explore how speed, reaction time, and road surface determine the difference between safety margin and collision.
* Trafikverket's standard theory calculations assume a normal driver at 1.0 second.
Trafikverket rule of thumb:
(70 / 10) × 3 × 1.0s
= 21 meters
Distance traveled at constant speed before your foot touches the brake pedal.
Physics formula:
70² / (250 × 0.8)
= 24.5 meters
Note quadratic increase: doubling speed results in 4 times longer braking distance!
Stopped with undefined meters margin before the obstacle.
Stopping distance is the sum of reaction distance and braking distance.
Trafikverket B-Theory Tips
• Quadratic Rule (Speed vs Braking Distance)
If speed increases by a factor, braking distance increases by that factor squared. Increasing speed from 50 to 100 km/h (2x) increases braking distance 2² = 4 times!
• Friction & Slipperiness
On glaze ice (f = 0.1), braking distance can be up to 8–10 times longer than on dry asphalt. Lowering speed is the only way to counteract this.