Speed Limits and Safe Following Distance
Posted Limits and Basic Speed Law
Speed limits set the maximum lawful speed under good conditions - they never obligate you to drive that fast. The basic speed law requires you to drive at a speed reasonable and prudent for existing conditions, which means snow, ice, fog, rain, heavy traffic, or darkness can make the posted limit unsafe. Alaska's default urban limit is 25 mph unless posted otherwise, and speed limits are lower in school zones and residential areas.
Following Distance
The classic rule is the three-second following distance: pick a fixed object ahead, and when the vehicle ahead passes it, count seconds until you pass it. Three seconds is the minimum for ideal conditions; increase to four or more in rain, and much more on ice or snow. In Alaska winter conditions, doubling or tripling following distance is standard practice. A useful supplement is the two-second-plus rule at higher speeds.
Adjusting for Conditions
Speed should drop for curves, hill crests, work zones, wildlife corridors, and reduced visibility. Work zones often post reduced limits that are enforceable even when workers are absent. Slow-moving vehicles (farm equipment, snow plows) require patience, not tailgating.
Traps to Watch
Questions often present a posted limit with bad weather and ask the safe speed - the answer is below the posted limit. Another trap is treating the three-second rule as fixed regardless of conditions; it is a minimum, not a target. Watch for questions about minimum speed limits on freeways and about the difference between absolute and basic speed laws.
Rule of Thumb
Three seconds in good weather, more in bad, and never faster than conditions allow - the posted sign is a ceiling, not a goal.