Speed and Space Management
Speed and Space Management tests speed selection, stopping distance, space cushions, and safe following. The exam looks for judgment, not just knowledge of posted limits.
Core rules
- Never exceed the posted limit or a safe speed for conditions; the basic speed law requires a speed that lets you stop within the assured clear distance ahead.
- Total stopping distance is perception distance plus reaction distance plus braking distance. It rises with speed, load, wet or icy pavement, and poor brake condition.
- Keep a space cushion ahead, at the sides, and behind. Avoid traveling in packs.
- At 55 mph, a vehicle covers about 80 feet per second. A 3-second gap is about 240 feet; a 4-second gap is about 320 feet.
- When entering or exiting a highway, signal, check mirrors and blind spots, and adjust speed to merge safely.
Worked example
At 55 mph, 55 × 1.47 ≈ 80.9 feet per second. A 3-second following gap is about 243 feet; a 4-second gap is about 324 feet. A loaded truck needs more braking distance, so the 4-second gap is the safer minimum.
Traps
Using a fixed car-length gap; tailgating to prevent cut-ins; ignoring speed gain on a downgrade; following too closely in rain or fog.