CDL Air Brakes
Fail this and an L restriction bars you from any vehicle with air brakes, which is most of them.
20 questions, 16 correct to pass. The federal standard is 80 percent on every commercial knowledge exam, so that is the bar used here.
Answer, see the explanation and the source straight away, and keep moving. Missed questions save to your review deck automatically.
Other CDL knowledge areas
General Knowledge
Required of every applicant: inspection, control, space and speed management, hazard perception, emergencies and hours of service.
Combination Vehicles
Coupling, the fifth wheel, off tracking and trailer swing. Needed for Class A.
Hazardous Materials
Placards, shipping papers, segregation and the security threat assessment.
Tank Vehicles
Liquid surge, baffles, outage and why a tanker rolls over so readily.
Doubles and Triples
Rearward amplification, converter dollies and coupling a second or third trailer.
Passenger Transport
Bus inspection, standee lines, passenger supervision and railroad crossings.
School Bus
Danger zones, loading and unloading, student crossing and evacuation.