Speed Limits and Safe Following Distance
Choosing a safe speed
Posted limits are maximums for ideal conditions, not targets. You must drive at a speed reasonable for weather, visibility, road surface, traffic density, and your own visibility - the "basic speed law" or "safe speed rule." Common default limits in residential and business districts cluster around 25-30 mph, but always follow posted signs. School zones, work zones, and some residential areas carry reduced limits that apply only during specified hours; questions often test whether you noticed the qualifying plaque.
Following distance is best managed with the three-second rule: pick a fixed object ahead, and when the vehicle ahead passes it, count "one-thousand-one, one-thousand-two, one-thousand-three." If you reach the object before finishing, you are too close. Add a second for rain, a second or more for snow or ice, and more for heavy vehicles, motorcycles, or when being tailgated (increase space ahead so you can brake gradually).
Minimum following distances also appear in law for specific situations: behind emergency vehicles, in tunnels, and when following vehicles that must stop at railroad crossings.
Trap: a question may ask for the minimum following distance "in good conditions" (three seconds) versus "in rain" or "behind a motorcycle" (more). Another trap is asking whether you may exceed the posted limit to pass - generally no, except where a specific statute permits it.
Worked example: At 60 mph you travel about 88 feet per second, so a three-second gap is roughly 264 feet - nearly the length of a football field. In rain, that becomes four seconds, about 350 feet.