Lesson 2.1 — Speed Management

Why this matters

Speed is the single largest contributor to the Unsafe Driving CSA score. Speed violations span four codes — 6-10 over, 11-14 over, 15+ over, and work-zone speeding — and together they account for a major share of all roadside citations issued to CMV drivers.

Speed is a CDL killer. 15+ mph over is a "serious traffic violation." Two in three years = 60-day CDL suspension. Three = 120-day suspension. You don't drive. You don't get paid.

And the physics: a loaded tractor-trailer at 55 mph needs about two football fields to stop on dry pavement. Add rain and it doubles. The speed limit isn't the goal — it's the ceiling.

1 Posted limit

The number on the sign. Many states post a lower truck speed — California is 55 mph for trucks on most interstates while cars do 65. Read the truck sign, not the car sign. If you don't see a truck sign, the posted limit applies to you.

Cruise 3 mph below the limit. That way a small downhill gain doesn't push you over, and you have a buffer for the radar gun's tolerance.

2 Speed for conditions (49 CFR 392.14)

This is the rule drivers miss most. The posted limit is the maximum safe speed in perfect conditions. Anything less than perfect, you slow down.

• Wet pavement: drop 10 mph.
• Heavy rain or fog: drop 20 mph.
• Snow or ice: drop 30+ mph or stop entirely.
• Strong crosswind on a high trailer: drop 10–15 mph.
• Heavy traffic, congestion, urban: drop to the speed of traffic.

49 CFR 392.14 specifically says: "Extreme caution in the operation of a commercial motor vehicle shall be exercised when hazardous conditions . . . adversely affect visibility or traction. Speed shall be reduced when such conditions exist."

If conditions get bad enough, you stop driving. Only the driver — not dispatch, not the carrier — can decide it's not safe to operate.

3 Work zones

Work zone speeding is the most expensive speed citation. Most states double the fine. Some add a separate state-level violation on top of the federal CSA points.

The rule:

• Work zone signs (orange, diamond-shaped) start well before the actual work.
• Posted work zone speed applies even when no workers are present.
• Reduce another 10 mph below the work zone posted limit if there's any uncertainty.
• If lanes shift, sit at the slowest gear you can sustain — don't try to maintain interstate speed through narrow lanes.

4 Downgrades

Mountain grades kill brakes and kill drivers. The technique is snub braking:

1. Before the descent — downshift to a low gear (one or two below the gear you climbed in). Reduce speed at the top.
2. Engage the engine brake or Jake brake.
3. Let the truck accelerate to 5 mph above your chosen safe speed (e.g. 35 mph).
4. Apply the service brakes firmly until you drop to 5 mph below safe speed (e.g. 30 mph).
5. Release the brakes completely. Let them cool. Repeat as needed.

Never ride the brakes. Continuous light pressure overheats the drums, the brakes fade, then there are no brakes at all. The Lakewood, Colorado runaway in 2019 killed four people because the driver rode the brakes.

"I was just keeping up with traffic" — not a defense. The CMV speed limit applies to you, not the cars.

"My cruise was set at the limit" — cruise control on a downhill grade will let speed climb 5+ mph before disengaging. Watch your speedometer, not the cruise display.

"The work zone was empty" — irrelevant. Work zone speed applies whether or not workers are present.

"I was going 65 in a 55" — that's 392.2-SLLS3, 7 CSA points, and a serious traffic violation flag if it's 15+. Two of these in three years = 60-day disqualification.

Tailgating at speed — even at the posted limit, riding the bumper of the vehicle in front of you is aggressive driving and a separate citation.

1. Cruise 3 mph under the posted limit. The buffer absorbs slope, wind, and radar-gun tolerance.
2. When in doubt, slow down. No load matters more than your CDL.
3. Rain = minus 10 mph. Fog or snow = minus 20. Memorize these.
4. Work zone = minus 10 from the work-zone limit. Empty or not.
5. Snub-brake every downgrade. Lower gear at the top. Hard short brake. Release. Cool. Repeat.
6. If a dispatcher pressures you to make up time — that's coercion under 49 CFR 390.6. Document it. Refuse it. Drive your safe speed.

• ○ 5 mph over
• ○ 10 mph over
• ✓ 15 mph over
• ○ Any amount in a work zone

• ○ 65 mph — the posted limit applies
• ○ About 55 mph — drop 10 mph for wet pavement
• ✓ About 45 mph — drop 20 mph for heavy rain and wet pavement
• ○ 70 mph — the rain has cleared the truck off the radar

• ✓ The 45 mph work zone speed applies — workers do not need to be present
• ○ You may drive the regular posted speed since no workers are visible
• ○ 55 mph is allowed in empty work zones
• ○ Work zone speed only applies when workers are within 50 feet

• ○ Continuous light pressure on the brakes
• ✓ Choose a safe speed; let it climb 5 mph above; brake hard until 5 mph below; release; repeat
• ○ Use the parking brake to slow down
• ○ Shift to a higher gear at the bottom

• ○ You must comply — dispatchers have authority to set the speed
• ✓ Only the driver can decide what is safe — coercion to violate safety rules is prohibited under 49 CFR 390.6
• ○ You can do it if you stay under 15 over
• ○ You must speed only on interstates