Speed Limits, Following Distance, and Safe Driving Behavior
What this domain tests
Speed and following-distance questions test whether you can choose a speed that lets you stop within the distance you can see and react. They also test the three-second rule and the effect of rain, darkness, and heavy loads.
Core rules
- Default limits: in Liberia, built-up areas are commonly limited to about 25 mph and rural highways to about 45 mph unless a sign says otherwise. School zones, work zones, and dangerous bends often require 15 mph or less. A posted lower limit always overrides the default.
- Basic speed law: never drive faster than is safe for conditions, even below the posted limit. Wet roads, poor visibility, and pedestrians require slower speeds.
- Following distance: use at least three seconds behind the vehicle ahead in good, dry conditions. Add one second for rain, one for darkness, and more when following a truck or motorcycle. In heavy rain, double the gap.
- Stopping distance is thinking distance plus braking distance. It rises with speed and much more on wet roads.
Worked example
You are doing 45 mph on a dry road. At 45 mph you travel 66 feet per second, so a three-second gap is about 198 feet, roughly 15 car lengths. In rain, brake response worsens, so use at least four seconds, about 264 feet. If a truck ahead blocks your view, increase further; you need to see past it, not just follow its taillights.
Traps
Using a two-second gap at highway speed; tailgating to save time; believing a speed limit is a target in rain; and ignoring lower school-zone limits when children are present.