What is the fundamental speed law and how should you adjust your speed?

• A. Drive at a speed that is safe for road, weather, traffic, and visibility; do not exceed posted limits and adjust for conditions.
• B. Always drive at the posted speed limit.
• C. Increase your speed in poor weather.
• D. Drive as fast as other vehicles.

Answer: (A)

Speed should be chosen to match road conditions, weather, visibility, and traffic, while staying within posted limits. This means you adjust your speed downward when conditions are harsher—rain, ice, snow, fog, or nighttime glare reduce traction and reaction time, so a slower, more controlled pace helps you stop safely and avoid skidding or losing control. It also means you consider how many cars are around you and how quickly they’re moving; you can’t safely travel at the maximum limit if other drivers are braking suddenly or if there are pedestrians, cyclists, or limited sight lines ahead. Posted speed limits are maximums for ideal conditions, not guarantees of safety in poor ones.

Choosing to drive at the posted limit in bad weather or low visibility can lead to longer stopping distances and reduced control. Increasing speed in poor weather further decreases traction and reaction time, making crashes more likely. Following the traffic exactly by matching everyone else’s speed can still be unsafe if that flow includes drivers who aren’t adjusting for conditions. The safest approach is steady, deliberate speed that respects the conditions and keeps you, and others, out of danger.