Space Management
Space management is the exam's way of testing whether you leave room to stop, turn, or absorb another driver's mistake. It covers following distance, side and rear space, overhead clearance, and lane position.
Following distance
Use one second for each 10 feet of vehicle length, then add one second if you are over 40 feet, and another second above 55 mph. A 40-foot bus needs 4 seconds at 40 mph; a 70-foot combination at 55 mph needs 7 seconds. This is not the two-second car rule. In rain, snow, or darkness, double it. If someone cuts in, drop back rather than tailgate.
Side, rear, and overhead
Avoid driving alongside another vehicle; a tire blowout or lane drift leaves no room. If you are tailgated, increase the space ahead so you can stop gradually, and let the tailgater pass when safe. Know your height: most routes allow 13 feet 6 inches to 14 feet, but bridges and tree limbs vary. Watch clearance signs and know your actual loaded height. Keep space behind by signaling early and braking smoothly.
Worked example
A 70-foot tractor-trailer travels at 55 mph. One second per 10 feet is 7 seconds, and the over-55 rule adds one more, so the target is 8 seconds. At 55 mph the vehicle covers about 80 feet per second, so 8 seconds is roughly 640 feet - more than two football fields. If a car passes and pulls in 100 feet ahead, you are 540 feet short of the target; ease off.
Traps
Using a fixed two-second gap; tailgating to stop cut-ins; ignoring overhead clearance; and failing to add space in rain or at night.