Gross Vehicle Weight Rating (GVWR)
The maximum allowable total weight of a single vehicle when fully loaded.
Gross Combination Weight Rating (GCWR)
The maximum allowable loaded weight of a combination vehicle (tractor plus trailer).
Air Brake Lag
The delay (approx. 0.5 seconds) for air pressure to travel through lines to activate brakes.
Spring Brakes (Emergency Brakes)
Mechanical springs that automatically apply the brakes if air pressure is lost.
The Kingpin and Locking Jaws
The main connection point locking the trailer to the tractor's fifth wheel.
Glad Hands
Hose couplers connecting the tractor's air brake system to the trailer.
The 14-Hour Rule
The maximum daily window a commercial driver can drive and perform work.
Hazardous Materials Placards
Diamond-shaped warning signs placed on all four sides of a vehicle carrying hazardous cargo.
Pre-Trip Inspection Checklist
A safety check of all critical parts (steering, suspension, brakes, engine) before driving.
Tanker Baffles vs. Smooth Bores
Bulkheads inside liquid tanks designed to control liquid surge.
Select a Concept to Read
Click on any concept card on the left to read its full explanation, visual guides, and test sample questions.