General Knowledge: Inspection, Control, and Safety
Maryland's CDL General Knowledge domain tests the core skills that apply to every commercial vehicle: pre-trip inspection, basic control, shifting, backing, speed and space management, hazard perception, emergency procedures, railroad crossings, night and mountain driving, fatigue, and alcohol and drugs. The questions reward procedures you can explain step by step, not just definitions.
Inspection, control, and shifting
A pre-trip inspection is a systematic check of the engine compartment, walk-around items, lights, brake components, tires, coupling, and emergency equipment. During the Maryland skills test you must say what you are checking and why. For control, start in the correct gear, release the parking brake only after you are ready, and avoid coasting. Progressive shifting uses lower rpm and saves fuel; downshift before a downgrade so you are not braking and shifting at the same time.
Speed, space, and following distance
The CDL following-distance rule adds one second for each 10 feet of vehicle length at speeds below 40 mph, and one extra second above 40 mph. Worked example: a 60-foot combination traveling 55 mph needs 6 seconds for length plus 1 second for speed, or 7 seconds. Pick a fixed object, count when the vehicle ahead passes it, and adjust for rain, darkness, or a heavy load.
Hazards and emergencies
Scan 12 to 15 seconds ahead, check mirrors every 5 to 8 seconds, and cover the brake at stale green lights. If a tire blows, hold the wheel, avoid hard braking, and slow gradually. Never stop on railroad tracks; if the gate comes down, drive through the gate rather than stall on the crossing. Fatigue and alcohol are safety domains: a CMV driver is prohibited at 0.04% BAC or higher, and fatigue must be managed with rest, not caffeine.
Traps
Holding the clutch while stopped, oversteering while backing, using engine brakes on slippery surfaces, treating 0.04% as a legal limit instead of a violation threshold, and forgetting to recheck mirrors before changing lanes.