Vehicle Inspection and Basic Control
The DC CDL General Knowledge exam opens with this domain: what federal rules require you to confirm before moving, how to set the seat and mirrors so you can actually see, and what to feel for in the first mile. Questions are situational - a gauge reading, a mirror image, a symptom that appears at 5 mph.
Before the wheels turn
- 49 CFR 392.7 requires you to be satisfied the vehicle is in safe operating condition before driving; 392.9 covers cargo. Neither is optional.
- Seat: press the clutch or brake to the floor and keep a slight bend in the knee; reach the top of the wheel without stretching; grip at 9 and 3, hands outside the rim.
- Mirrors: set flat mirrors so a sliver of the vehicle body shows, then aim the rest down the lane. Convex mirrors widen the view but make objects look smaller and farther away than they are.
- Secure loose items in the cab; a thermos becomes a projectile in a panic stop.
First minute with the engine running
- Oil pressure should register within seconds. If the gauge stays at zero, shut down and find out why rather than waiting for it to clear.
- Let air pressure build to governor cut-out and confirm the low-pressure warning works.
- Brake check at about 5 mph: rolling slowly, apply the brakes. Pulling, grabbing, or a spongy pedal means stop and inspect.
Putting the vehicle in motion
- Signal, check mirrors and blind spots, release the parking brake fully, and accelerate smoothly.
- Use pull-push steering for sweeping turns instead of crossing your arms.
- Look far ahead and brake early; avoid fanning air brakes, which wastes air you may need later.
Worked example
A driver starts a cold tractor. The low-air buzzer sounds and the oil pressure gauge sits at zero. Reasoning: the buzzer is normal at start with air depleted, but zero oil pressure is not. Shut the engine down and check oil level and the gauge circuit - an engine can be damaged in seconds. Once oil pressure is normal, build air to cut-out, then perform the 5 mph brake check before leaving the yard.
Traps
- Treating the walk-around as the whole inspection; seat, mirrors, belts and gauges are testable in-cab items.
- Believing convex mirrors give true distance.
- Skipping the low-speed brake test because the tractor has ABS.