Virginia CDL — Air Brakes practice
Speed & Space Management
Choosing a safe speed, keeping a space cushion, adjusting for weather and traffic, and understanding stopping distance.
Questions reviewed against the official Virginia driver handbook · July 7, 2026
2 questions · pass with 2 correct. You get instant feedback and an explanation after every answer.
Study questions with answers
2 sample Speed & Space Management questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.
1. Compared with hydraulic brakes, why do air brakes add extra stopping distance called brake lag?
Correct answer: Air takes about a half second or more to reach the brakes
Hydraulic brakes act almost instantly, but air needs about a half second or more to travel through the lines to the brakes, which adds roughly 32 feet at 55 mph on dry pavement.
Source: Virginia Commercial Driver's License Manual, Section 5 (Air Brakes), 5.4.4 Stopping Distance
2. What are the four elements that make up total stopping distance for an air-brake vehicle?
Correct answer: Perception, reaction, brake lag, and braking distances
Air-brake vehicles add brake lag to the usual factors, so total stopping distance is perception distance plus reaction distance plus brake lag distance plus braking distance.
Source: Virginia Commercial Driver's License Manual, Section 5 (Air Brakes), 5.4.4 Stopping Distance
More CDL — Air Brakes topics
Practice Speed & Space Management in another state
Every Virginia question is written from the official Virginia driver handbook and checked against its current edition. DMV Test Free is a free, independent study resource — not affiliated with any DMV or government agency. About DMV Test Free