Stopping Distance Calculator
Calculate total stopping distance — reaction time + braking — based on speed, road conditions, and vehicle factors.
| Speed | Dry (ft) | Wet (ft) | Icy (ft) |
|---|
Table uses average car, good tires, ABS equipped, ~1.0s reaction time.
The 3-Second Following Rule
Pick a fixed object on the road. When the car ahead passes it, count "one-thousand-one, one-thousand-two, one-thousand-three." If you pass the same object before you finish counting, you are following too close. On wet roads, double it to 6 seconds. On icy roads, use 10+ seconds.
Why Speed Doubles Stopping Distance
Kinetic energy equals ½mv². Doubling your speed quadruples the kinetic energy your brakes must dissipate. Going from 30 mph to 60 mph doesn't double stopping distance — it roughly quadruples the braking component. This is why highway speed crashes are so much more severe than low-speed crashes.
How ABS Works
Anti-lock Braking System (ABS) rapidly pulses brake pressure — up to 15 times per second — to prevent wheel lockup. A locked wheel loses steering ability and actually increases stopping distance on most surfaces. ABS maintains wheel rotation so you can steer around an obstacle while braking. On dry pavement the difference is modest; on wet or icy roads, ABS can shorten stopping distance by 20–30% while preserving steering control.
Winter Tire Benefits
All-season tires lose grip below 45°F because the rubber compound hardens. Winter tires use a softer compound and specialized tread designed to stay pliable and channel snow. On ice, winter tires can reduce stopping distance by 30–40% compared to all-season tires. No set of tires overcomes the physics of ice — always increase following distance in winter conditions.