CDL questions and answers
- Q1. What is the minimum following distance for a CMV at highway speeds in good conditions?
Answer: At least 7 seconds (1 second per 10 ft of vehicle length, plus extra for weather). FMCSA §392.22 (2026).
- Q2. When must you stop before crossing railroad tracks?
Answer: Always, for any CMV placarded for HazMat — within 15 ft but not less than 50 ft from the nearest rail. FMCSA §392.10 (2026).
- Q3. How often are you required to inspect your CMV?
Answer: Pre-trip inspection before every trip; en-route inspection every 2 hours or 100 miles; written post-trip inspection report at the end of every shift. FMCSA §396.11 (2026).
- Q4. What is the legal blood alcohol concentration (BAC) for a CMV driver?
Answer: 0.04% — half the non-commercial limit. FMCSA §382.201 (2026).
- Q5. Maximum driving hours per shift?
Answer: 11 hours driving within a 14-hour on-duty window, after 10 consecutive off-duty hours. FMCSA §395.3 (2026).
- Q6. What does a diamond-shaped placard on a tanker indicate?
Answer: A hazardous material load; class is identified by the four-digit UN number. 49 CFR §172.504 (2026).
- Q7. When are you required to use hazard lights while parked on the roadway?
Answer: When stopped on the traveled portion or shoulder of a highway — except when using emergency flares or reflectors in a built-up area. FMCSA §392.22 (2026).
- Q8. What is the minimum tread depth for steer tires on a CMV?
Answer: 4/32 inch (3 mm) on steer tires; 2/32 inch on other positions. FMCSA §393.75 (2026).
- Q9. How do you check the air system for leaks during a pre-trip inspection?
Answer: Build pressure to governor cut-out (typically 120–140 psi), shut off the engine, observe the pressure drop — single vehicles must hold ≥3 psi/min; combinations ≥5 psi/min. Texas CMV Handbook, Ch. 5 (2026).
- Q10. What is an "emergency braking" distance vs. "normal stopping" distance?
Answer: Perception-reaction (1.25 s) + brake lag (0.5 s) + braking distance; at 60 mph in a loaded tractor-trailer, total stopping distance is roughly 300 ft. FMCSA braking distance study (2026).
- Q11. If your CMV becomes disabled on a highway, where should you place reflective triangles?
Answer: 10 ft, 100 ft, and 200 ft behind the vehicle in the direction of oncoming traffic. Within 10 minutes. FMCSA §392.22 (2026).
- Q12. What does "bridge formula" limit?
Answer: Maximum gross weight a CMV can carry on consecutive axles based on axle spacing — protects bridges. 23 CFR §658.17 (2026).
- Q13. When is a CDL driver exempt from the ELD mandate?
Answer: Drivers operating within a 150 air-mile radius and returning to base each day, pre-2000 model-year vehicles withoutELDs, and short-haul drivers who keep paper logs. FMCSA §395.1 (2026).
- Q14. What is the maximum width of a CMV on an interstate?
Answer: 102 inches (8.5 ft) standard; some states allow 102 inches plus appurtenances. 23 CFR §658.15 (2026).
- Q15. How long can a CDL driver be on duty without 10 consecutive off-duty hours?
Answer: The 14-hour on-duty window cannot be extended. After 14 cumulative hours on duty, the driver must take 10 consecutive off-duty hours, even if only 6 hours of driving occurred. FMCSA §395.3 (2026).
- Q16. What is the difference between "intrastate" and "interstate" commerce?
Answer: Intrastate: trade entirely within Texas, regulated by DPS but not FMCSA hours-of-service. Interstate: crosses state lines, falls under full FMCSA rules including 11/14-hour limits. FMCSA §390.5 (2026).
- Q17. What is the correct procedure for a downgrade request after a disqualifying offence?
Answer: File the CDLIS Voluntary Withdrawal / Downgrade form with Texas DPS; the driver surrenders the CDL and receives a Class C licence for the disqualification period. Texas DPS Driver License Office (2026).
- Q18. When are you required to place a fire extinguisher on a CMV?
Answer: All CMVs carrying passengers or placarded HazMat must carry a UL-listed 5-B:C extinguisher, fully charged, accessible to the driver. FMCSA §393.95 (2026).
- Q19. What is the "gross combination weight rating" (GCWR)?
Answer: The total weight of the powered unit plus trailer(s) plus load, as designated by the manufacturer. Class A requires GCWR > 26,001 lb. FMCSA §383.5 (2026).
- Q20. If you are convicted of a DUI in your personal vehicle, does it affect your CDL?
Answer: Yes — a personal-vehicle DUI is treated as a CDL disqualification; first offence = 1-year disqualification, second = life. FMCSA §383.51 (2026).
Pass-mark and score interpretation
The Texas DPS scores each knowledge test independently; you must clear 80% on every test taken. A combined "average" pass is not permitted (Texas DPS, 2026). Retake rules: each retest requires a 1-business-day wait for the same test; the CLP must remain valid throughout.
Where to book the Texas CDL test
Book through the Texas DPS online scheduler (txapps.texas.gov/DPS-CDLScheduling) or walk in to a CDL-designated office. Bring: Texas CLP, DOT medical card, Social Security card, two proofs of Texas residency, and a Class A/B/C training certificate (if applicable). The base fee is $61 plus $10 per endorsement (Texas DPS, 2026).
Resources and next steps
After passing the Texas knowledge and skills tests, you can add HazMat, Tanker, Doubles/Triples, or Passenger endorsements as needed for your job. Pair your study with the free TutorsBot entrance-exams hub for cross-cluster practice, and bookmark the FMCSA CDL Manual for any rule citation. For cybersecurity awareness on the road, see our sibling guide on spotting phishing emails that target dispatchers and fleet managers.
Photo: NASA, Public Domain (NASA), via NASA Image and Video Library (https://images.nasa.gov/details/KSC-2012-4570)
Fazlur Rahman
