What is the 3-second rule in driving?

A following-distance check: when the vehicle ahead passes a fixed object, count three full seconds — if you arrive before finishing, you're too close. Add seconds for rain, night, fog, or ice.

What is the speed limit when there's no sign?

Your state's default limit for that road type applies — commonly 25–30 mph in residential and business areas and 55 or more on rural highways. The permit test expects you to know your state's defaults.

How far does it take to stop at 60 mph?

Around 300 feet on dry pavement once perception, reaction, and braking are added together — roughly a football field. Wet or icy roads multiply that.

Speed Limits and Following Distance: The Numbers That Matter

Speed questions on the permit test come in two flavors: law questions (what's the limit here?) and physics questions (how long does stopping actually take?). Both reward the same insight — posted numbers are ceilings for perfect conditions, and space is the only thing that buys you reaction time.

The basic speed law

Every state has some version of it: never drive faster than is safe for current conditions, regardless of the posted limit. Rain, fog, ice, traffic, and darkness all lower the real legal limit below the sign. You can be ticketed doing 55 in a 55 if 55 was unsafe in that moment — a fact the test states outright and students refuse to believe.

Default limits worth memorizing

Exact numbers vary by state, but the pattern is consistent, and your state page lists its specifics. Typical defaults: 15–25 mph in school zones when children are present, 25–30 mph in residential and business districts, 55–70 mph on highways. When no sign is posted, your state's default for that road type applies — 'I didn't see a sign' is an answer choice, never the answer.

The three-second rule

Pick a fixed object — a sign, a shadow, an overpass seam. When the car ahead passes it, count 'one-thousand-one, one-thousand-two, one-thousand-three.' If you reach the object first, you're following too closely. The beauty of counting time instead of car lengths is that it scales with speed automatically.

Three seconds is the dry-pavement minimum. Rain, night, fog, gravel, or a tailgater behind you: stretch it to four or more. Ice or snow: six seconds and beyond. When someone tailgates you, add space in front — your following distance has to cover both of you now.

Total stopping distance

Stopping = perception + reaction + braking. At 60 mph you cover 88 feet per second, and a typical 1.5 seconds of perceiving-plus-reacting spends over 130 feet before the brakes engage. Add braking and total stopping distance runs around 300 feet — the length of a football field. Doubling your speed roughly quadruples braking distance, which is why 'twice as fast, twice the stopping distance' is always a wrong answer on the test.

Now make it stick

Reading builds recognition — answering builds recall. Drill this topic with original practice questions and full explanations.

Practice Speed & Space questions

Frequently asked questions

What is the 3-second rule in driving?: A following-distance check: when the vehicle ahead passes a fixed object, count three full seconds — if you arrive before finishing, you're too close. Add seconds for rain, night, fog, or ice.
What is the speed limit when there's no sign?: Your state's default limit for that road type applies — commonly 25–30 mph in residential and business areas and 55 or more on rural highways. The permit test expects you to know your state's defaults.
How far does it take to stop at 60 mph?: Around 300 feet on dry pavement once perception, reaction, and braking are added together — roughly a football field. Wet or icy roads multiply that.