Driving Safely
Driving Safely
The Driving Safely domain tests whether you can see hazards early, choose a safe speed and following distance, and recover from emergencies without losing control. New Mexico's general knowledge exam draws these items from the federal CDL standard, so expect CMV-specific numbers rather than car-driving rules.
Space and speed
Use the following-distance rule for CMVs: one second for each 10 feet of vehicle length, plus one extra second at speeds above 40 mph. Scan 12 to 15 seconds ahead, check mirrors often, and adjust for rain, fog, curves, and heavy traffic. At night, drive so you can stop within the distance your headlights show.
Worked example
A 60-foot tractor-trailer travels at 55 mph. Base following distance is 6 seconds; because 55 mph is above 40 mph, add 1 second, for 7 seconds. If the vehicle ahead passes a sign, you should not reach that sign for at least 7 seconds.
Emergencies
For a rear-wheel skid, release the brakes and steer in the direction you want the front of the vehicle to go. For a front-wheel skid, ease off the steering and slow gradually. If a tire fails, hold the wheel firmly, keep the vehicle straight, and avoid hard braking. If the service brakes fail, downshift, use engine braking, and apply the parking brake gradually.
Traps that cost marks
- Applying the 4-second car rule to a 60-foot CMV.
- Braking hard during a tire blowout.
- Stopping on railroad tracks because traffic ahead is backed up.
- Assuming a 0.04% BAC limit is the same as the 0.08% limit for private cars.