CDL Prep is the best way to prepare for the Commercial Drivers License General Knowledge, and various endorsement exams. CDL Prep contains questions on the following topics: General Commercial, Air Brakes, Combinations, Hazmat, Passenger, Tanks, School Bus, and Doubles/Triples. Features: 1. Over 500 questions to practice with. 2. Exam Mode - 60 minutes to answer 50 randomly chosen questions ...