Space Management: Cushions Ahead, Behind, and Beside
Space Management tests the following-distance formula, side and rear cushions, and what to do when another driver takes your space.
Following distance
- One second for every ten feet of vehicle length at speeds under 40 mph, plus one extra second above 40 mph. A 60-foot rig therefore needs six seconds under 40 and seven above.
- Double the gap in bad weather, at night, or when visibility is limited.
- If someone cuts in, drop back to rebuild the gap rather than holding it.
Space to the sides and behind
- Avoid riding alongside another vehicle. Pass briskly or drop back.
- If a tailgater is close, increase your own following distance so you can slow gradually instead of braking hard.
- When being passed, hold your lane and your speed, or ease off slightly.
Worked example
You are driving a 65-foot combination at 55 mph when a car merges in front, leaving about two seconds. You need roughly seven seconds above 40 mph. The right response is to lift off the throttle and let the gap reopen gradually, not to brake sharply, because whoever is behind you is likely following at two seconds as well.
Traps that cost marks
- Applying the passenger-car three-second rule unchanged.
- Speeding up while being passed.
- Holding a gap a merging car has already claimed.
- Forgetting that the extra second applies only above 40 mph.