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7 topics
General Knowledge
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Quick Reference Cheat Sheet 📋
The numbers, limits, and rules you absolutely must have memorized. Lemon-highlighted = most commonly tested.
🚛 Vehicle Sizes & Weights
- CDL required: 26,001+ lbs GVWR
- Class A: combo vehicle 26,001+ lbs; towed vehicle over 10,000 lbs
- Class B: single vehicle 26,001+ lbs
- Class C: 16+ passengers OR HazMat
- Max legal weight (federal): 80,000 lbs
- Single axle limit: 20,000 lbs
- Tandem axle limit: 34,000 lbs
⚡ Class A = Any combo. Class B = Big single truck. Class C = People or HazMat.
⏱️ Hours of Service
- 11 hours driving after 10 consecutive off-duty hours
- 14-hour driving window (on-duty limit)
- 30-minute break required after 8 hours driving
- 60/70 hour rule: 60 hrs/7 days OR 70 hrs/8 days
- 34-hour restart: two consecutive 1am–5am periods
- Sleeper berth: can split 10-hr off duty (at least 8 hrs in berth)
⚡ 11 hrs drive / 14 hr window / 30 min break at 8 hrs
🛑 Braking & Stopping
- Normal stopping distance at 55 mph: ~335 feet
- Fully loaded trucks stop SLOWER than empty
- Air brakes: normal pressure 100–125 psi
- Low air warning: activates at 60 psi or below
- Spring brakes apply at 20–45 psi
- Never "fan" air brakes on long downhill grades
- Perception + reaction + braking = total stopping distance
⚡ Air brake check: leak rate should not exceed 3 psi/min
🔍 Pre-Trip Inspection Order
- 1. Engine compartment (oil, coolant, belts)
- 2. Cab interior (gauges, controls, mirrors)
- 3. Start engine (lights, warning lights)
- 4. Walk-around exterior (tires, lights, cargo)
- 5. Signal lights & brake check
- Front tire min tread: 4/32" · All others: 2/32"
⚡ Skills test: pre-trip, straight-line, offset, parallel, alley dock, road test
☣️ HazMat Basics
- 9 hazard classes (explosives, gases, flammable liquids, etc.)
- Placard required: 1,001+ lbs of a HazMat class
- Shipping papers: must be within reach when driving
- CHEMTREC: 1-800-424-9300 (emergency info)
- RR tracks: stop 15–50 feet before crossing
- Never transport forbidden or leaking materials
⚡ HazMat endorsement = knowledge test + TSA background check
🌀 Skids & Emergencies
- Rear wheel braking skid: release brakes, countersteer
- Front wheel skid: braking too hard OR too fast in turn
- Jackknife: trailer pushes cab sideways (release trailer brakes)
- Brake failure on downhill: use escape ramp, downshift, drag brakes
- Tire blowout: grip steering, controlled braking only after slowing
- Hydroplaning: ease off accelerator, don't brake hard
⚡ Most skids are caused by driving too fast for conditions
👥 Passenger / School Bus
- Passenger endorsement: Class P
- School bus endorsement: Class S
- School bus stop: 10 feet from railroad tracks minimum
- Must use mirrors to check for students around bus
- Never fuel with passengers on board
- Emergency exits: test must confirm all work properly
⚡ Load/unload students at least 10 feet from traffic
🔗 Combination Vehicles
- Longest combo: doubles/triples (Rocky Mountain doubles)
- Off-tracking: rear wheels follow a shorter path in turns
- Rearward amplification: trailer sways more than cab
- Pintle hook: connects doubles/triples converter dolly
- Tug test: pull forward with trailer brakes locked to confirm coupling
- Check glad hands, safety chains, and landing gear before moving
⚡ Converter dolly air tank drain valve must be CLOSED before coupling
🔢 Key Numbers to Memorize
- CDL weight threshold: 26,001 lbs
- Max gross weight: 80,000 lbs
- Normal air pressure: 100–125 psi
- Low air warning: 60 psi
- Spring brakes engage: 20–45 psi
- Max brake leak rate: 3 psi/min (single), 4 psi/min (combo)
- Following distance at highway speed: 1 sec per 10 ft of vehicle + 1 extra
- Stopping distance at 55 mph: ~335 ft
- Passing score on all IL CDL knowledge tests: 80%
⚡ These numbers appear on almost every CDL exam
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Topic Milestones
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MILESTONE 1
General Knowledge
The foundation of your CDL. Master this topic first — it covers everything from vehicle inspection to road safety and cargo rules.
🍋 Unlock when you pass at 80%+
Complete the General Knowledge quiz with 80%+ to unlock this milestone.
Am I Ready for the Real Test? ✅
Rate yourself honestly across 5 readiness categories. Takes about 3 minutes.