Controlling Speed
What the exam tests
Speed selection for conditions, load, and school-bus routes.
Core rules
- Never exceed the posted speed limit, and drive slower when conditions demand it.
- A loaded school bus needs more stopping distance than an empty one. Increase following distance and begin braking earlier.
- Slow down for curves, hills, wet or icy roads, fog, night, construction zones, and school zones.
- Use engine braking on long downgrades; do not ride the brakes.
- Do not use cruise control on wet, icy, or snowy roads, or in heavy traffic.
- At 55 mph, a heavy vehicle may need more than 300 feet to stop. At 20 mph, the distance is much shorter. Speed has a squared effect on stopping distance.
- School zone limits apply when children are present or when the sign states a time period.
Worked example
A driver is on a 55 mph rural road in light rain. The posted limit is 55, but the driver reduces to 45 mph and adds following distance. Reasoning: wet pavement reduces traction and increases stopping distance; the posted limit is a maximum for ideal conditions, not a target.
Traps that cost marks
Treating the speed limit as a minimum; following too closely at highway speed; using cruise control in rain; delaying braking until the last moment.