Space Management
This domain tests how you create and protect space around the vehicle-front, sides, rear, and overhead. The exam emphasizes escape routes and avoiding situations where you have no room to stop or maneuver.
Front, side, and overhead space
Maintain a following gap based on vehicle length and speed. Avoid driving beside other large vehicles; if you cannot see their mirrors, they cannot see you. When passing, do not linger alongside; complete the pass or drop back. Know your vehicle height and check posted clearance signs. If a clearance is not marked or looks doubtful, stop and verify rather than risk a bridge strike.
Lane position and traffic flow
Use lane position to increase visibility and space. When being passed, maintain speed and allow the other driver room to complete the pass. When entering traffic, do not force others to brake; wait for a safe gap. Leave room ahead at stops so you can steer around a stalled vehicle if necessary.
Worked example
You drive a 60-foot combination at 60 mph. The following time is 6 seconds for length plus 1 second for speed above 40 mph, or 7 seconds. At 60 mph, you travel about 88 feet per second, so the gap is roughly 616 feet. If traffic is heavy, increase it further. A 3-second gap would be only about 264 feet-far too little for a loaded combination.
Traps that cost marks
Following too closely to discourage merging; underestimating stopping distance; failing to check overhead clearance; and staying alongside another vehicle where you have no escape route. Also do not assume a posted clearance includes your load height.