Chapter 7 · Lesson 25 of 38
Tractor-trailers: size, braking and turning
4 min read · Safe Vehicle Operation
Explanation
Size. Without a special permit, a vehicle may be at most 8 ft 6 in wide, 13 ft 6 in high, and 80,000 lbs. Trucks and buses 80 inches wide or wider must have extra lighting markers and reflectors so their width shows at night.
Braking. A tractor-trailer takes longer to stop than a car at the same speed. At 55 mph an average car stops in about 130–140 feet (half a football field); a fully loaded tractor-trailer with hot brakes may need more than 400 feet. So never change lanes suddenly or stop in front of one.
Turning. A turning vehicle’s rear wheels follow a shorter path than its front wheels — the longer the vehicle, the bigger the difference. Truck drivers often swing out to make a tight turn. Watch a truck’s turn signals before passing, especially on the right: if it moves left, it may be setting up a right turn.
Lanes. On multi-lane highways, tractor-trailers stay in the center lane to help local traffic get on and off and to keep room to move over in an emergency.
Example
A semi ahead drifts left at an intersection. Its right signal is on. You stay behind it instead of squeezing past on the right, and it swings wide into the right turn.
Common mistake
Passing a truck on the right when it moves left at an intersection. It may be swinging out for a right turn — right into your path.
What the manual says
The average passenger car traveling at 55 miles per hour can stop in approximately 130 to 140 feet, or about half the length of a football field. A fully loaded tractor-trailer with hot brakes may take more than 400 feet to come to a complete stop, or more than the length of a football field.
Tractor-trailer drivers often swing out as the first step in making a tight turn.
When following a tractor-trailer, watch its turn signals before trying to pass, especially to the right.
Sources
- Manual p. 49
“The maximum width of any vehicle that may be operated without a special permit is eight feet and six inches. The maximum height of any vehicle that may be operated without a special permit is 13 feet, 6 inches. The maximum weight of any vehicle that may be operated without a special permit is 80,000 lbs.”
- Manual p. 49
“every truck or bus that is 80 inches in width or wider must have additional lighting markers, and reflectors that makes the vehicle visible.”
- Manual p. 50
“The average passenger car traveling at 55 miles per hour can stop in approximately 130 to 140 feet, or about half the length of a football field. A fully loaded tractor-trailer with hot brakes may take more than 400 feet to come to a complete stop, or more than the length of a football field.”
- Manual p. 50
“A tractor-trailer will take longer to stop than a car traveling at the same speed, and so you should not make a sudden lane change or stop in front of a tractor-trailer.”
- Manual p. 50
“With any turning vehicle, the rear wheels follow a shorter path than the front wheels, and the longer the vehicle is the greater the difference will be.”
- Manual p. 50
“Tractor-trailer drivers often swing out as the first step in making a tight turn.”
- Manual p. 50
“When following a tractor-trailer, watch its turn signals before trying to pass, especially to the right.”
- Manual p. 50
“tractor-trailers stay in the center lane to help the flow of local traffic on and off the highway.”
Check your understanding
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