Lesson 2.4 — Following Distance and Lane Discipline

Why this matters

Following too closely is the #1 contributor to rear-end crashes involving CMVs. A loaded tractor-trailer at 60 mph needs roughly two football fields of stopping distance — about 7 seconds of road. If you're closer than that, a sudden brake by the vehicle in front of you means a crash.

Code 392.2-FC (Following too close) carries 5 CSA points and is a documented item in the Unsafe Driving compliance category. Lane discipline violations (392.2-LV) carry the same weight and are easy to catch from overhead cameras and patrol aircraft.

This module is about space — the space in front, beside, and behind you. Space is the only thing that buys you time when something goes wrong.

The universal CDL standard. For every 10 feet of vehicle length, you need 1 second of following distance. Above 40 mph, add 1 second.

• Bobtail (tractor only) — 25 feet: 3 seconds below 40 mph, 4 seconds above.
• Standard tractor-trailer — 70 feet: 7 seconds below 40 mph, 8 seconds above.
• Doubles (two 28-ft trailers) — about 95 feet: 10 seconds.
• Triples (three 28-ft trailers) — about 125 feet: 12+ seconds.

Most of you are driving a standard tractor-trailer. The number is 7 seconds. Memorize it.

You don't need to estimate distance in feet. Count seconds instead.

1. Pick a fixed object on the side of the road — an overpass, a sign, a tree, a mile marker.
2. When the rear bumper of the vehicle in front of you passes the object, start counting.
3. Count slowly: "one-thousand-one, one-thousand-two, one-thousand-three..."
4. When your front bumper reaches the same object, stop counting.
5. If you reached it in less than 7 seconds, you are too close. Ease off the throttle.

Do this once every 5–10 minutes while driving. It becomes automatic after a few trips.

The 7-second rule is the minimum in dry, clear, daytime conditions. Anything less than perfect, add seconds:

• Rain or wet pavement: add 2 seconds (total 9).
• Heavy rain or fog: add 4 seconds (total 11+).
• Snow or ice: add 6+ seconds — or stop and wait.
• Night driving: add 2 seconds.
• Heavy load (near max gross weight): add 2 seconds.
• Construction, traffic, or unfamiliar route: add 2 seconds.

Conditions stack. Rain at night with a heavy load = 13+ seconds. That's no longer "following" — that's giving the car ahead its own ZIP code.

FMCSA recommends checking mirrors every 5 to 8 seconds. Set a mental rhythm. While you count following distance to the vehicle in front, glance at your mirrors.

Lane change sequence — every time:

1. Check mirror on the side you're moving to.
2. Signal (5 seconds before changing lanes on a highway, 3 seconds in town).
3. Check the mirror again — confirm the lane is still clear.
4. Move into the lane.
5. Check the mirror once more — confirm position and the vehicle behind.

Blind spots for a tractor-trailer:

• Directly behind the trailer — 200 feet of nothing-visible.
• Along the right side — 2 lanes wide, the length of the trailer.
• Along the left side — 1 lane wide, length of the trailer.
• 20 feet in front of the bumper — too low to see over the hood.

The right-side blind spot is the big one. Most no-zone crashes happen because a car moved into the right blind spot during a right lane change.

"Stay in your lane" sounds obvious but is one of the most-cited offenses. The three patterns inspectors document:

• Drifting — wheels crossing the lane line repeatedly. Suggests fatigue or distraction; can trigger a level III inspection on its own.
• Wide turns — entering an adjacent lane during a right turn. Sometimes unavoidable for a 53-ft trailer in a tight intersection, but document the route ahead.
• Lane restriction violation (392.2-LV) — using a lane prohibited to trucks. The most common form: "no trucks left lane" signs on multi-lane interstates in California, Pennsylvania, Indiana, and others.

When in doubt about a lane sign — take the right lane. The right lane is always legal for trucks except where specifically marked otherwise.

"I'm just keeping up with traffic" — irrelevant to following distance. The car ahead can stop in half your distance.

Tailgating to make a slower car move over — aggressive driving citation. Also dangerous; the car driver may panic-brake.

Someone tailgating you — let them pass. Don't speed up to "show them." Move right when safe.

Lane drifting — if your wheels touch the line repeatedly, an officer will assume fatigue or impairment. A drift across the white shoulder line is enough for a stop.

"I only do wide turns when I have to" — wide turns are still tickets if they go into another lane of traffic. Plan the route; some intersections are not survivable for a 53-ft trailer and need a different approach.

1. 7 seconds, always. Count it. If you reach the object before 7, ease off the throttle until you're at 7+.
2. More seconds for less than perfect. Rain +2. Fog or night +4. Snow or ice +6 or pull over.
3. Mirrors every 8 seconds. Set the rhythm. Front-left-front-right-front-left-front-right.
4. Lane change sequence: mirror, signal, mirror, move, mirror. Five steps. Every time.
5. Right lane unless you absolutely need to pass. Lane restriction violations are stupid and easy to avoid.
6. If a car tailgates you, let them pass. Move right when safe. Don't speed up. Don't brake-check.

• ○ 3 seconds
• ○ 5 seconds
• ✓ 7 seconds
• ○ 10 seconds

• ○ 3 seconds — slower speed reduces the need
• ○ 5 seconds — about the same as dry
• ○ 7 seconds — the rule does not change
• ✓ 9 seconds or more — add 2 seconds for wet pavement

• ○ Once a minute
• ✓ Every 5 to 8 seconds
• ○ Only when changing lanes
• ○ Every time you see a sign

• ○ Directly in front of the cab
• ○ Directly behind the trailer (about 200 feet)
• ✓ On the right side, 2 lanes wide and the length of the trailer
• ○ On the left side, 1 lane wide

• ○ Speed up to put distance between you
• ○ Brake-check them to back them off
• ✓ Maintain your speed and move to the right lane when safe to let them pass
• ○ Match their speed and ignore them