Speed Limits and Safe Following Distance
Choosing a Safe Speed
Minnesota's basic speed law says you must never drive faster than is safe for conditions, regardless of the posted limit. Posted limits are maximums, not targets. Common limits to know: 30 mph in urban districts, 55 mph on many two-lane rural roads, and 65-70 mph on rural interstates. School zones are typically 20 mph when children are present, and work zones carry doubled fines when workers are present.
Following distance is the most tested safe-driving concept. Use the three-second rule: pick a fixed object ahead, and when the vehicle in front passes it, count seconds until you pass it. Under three seconds means you are too close. Add a second for each adverse condition - rain, darkness, or a heavy load - and more for ice or fog. At highway speeds, three seconds translates to roughly one car length per 10 mph, but the time rule is more reliable because it adjusts for speed.
Stopping distance has three parts: perception distance (the time it takes you to notice a hazard), reaction distance (the time to move your foot to the brake), and braking distance. Total stopping distance grows with the square of your speed - doubling speed roughly quadruples braking distance. This is why speed-limit questions often ask about stopping distance rather than just the limit.
Trap: questions that ask whether you may exceed the posted limit to pass. The answer is generally no - you must stay within the limit even while passing.
Rule of thumb: three seconds in good weather, four or more in rain or dark, and much more on ice; slow down before you enter a curve or work zone, not in it.