Under 49 CFR 392.4, a driver who is under the influence of a controlled substance, other than one prescribed by a licensed medical practitioner who has advised the driver it will not affect safe driving, is:
- Allowed to drive if under the daily dose limit
- Allowed to drive only during daylight hours
- Prohibited from operating a commercial motor vehicle (correct)
- Required only to notify the dispatcher before driving
Controlled substances can impair alertness, judgment, and reaction time in ways the driver may not fully recognize in themselves. The rule removes that risk entirely by barring driving while under the influence, with a narrow exception for medication a doctor has confirmed is safe to drive on.
Source: 49 CFR 392.4.
Under 49 CFR 395.3, a property carrying driver whose carrier does not operate every day of the week may not drive after being on duty how many hours in 7 consecutive days?
- 50 hours
- 80 hours
- 60 hours (correct)
- 70 hours
The 60 hour in 7 day limit, or 70 hours in 8 days for carriers that operate daily, caps accumulated on duty time over a work week, not just a single shift. Fatigue can build up across several short duty periods even if no single day exceeds the daily limits, so a weekly cap is needed as well.
Source: 49 CFR 395.3(b).
Under 49 CFR 393.106, the aggregate working load limit of the tiedowns used to secure an article of cargo must generally be at least:
- 25 percent of the weight of the article
- 75 percent of the weight of the article
- 100 percent of the weight of the article
- 50 percent of the weight of the article (correct)
Cargo shifts under braking, cornering, and road irregularities, so the tiedowns have to be strong enough to resist those forces without failing. Setting the minimum combined strength at half the cargo's weight gives a working margin against the loads a moving vehicle actually produces.
Source: 49 CFR 393.106.
