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Question

Difficulty: MediumLarge Commercial Trucks and No-Zones

A fully loaded commercial tractor-trailer traveling at 55 mph under dry road conditions requires approximately the same distance to come to a complete stop as a standard passenger vehicle.

Answer: Answer

Answer

False
The statement is False. Under normal dry driving conditions at 55 mph, a fully loaded tractor-trailer takes nearly 400 feet to come to a complete stop—almost the length of a football field—compared to roughly 200 to 240 feet for a standard passenger car. This extended distance is caused by the truck's heavy mass, momentum, and the additional brake lag time inherent to air brake systems.

Step-by-Step Solution

1
Analyze vehicle mass and momentum factors
Determine that a fully loaded tractor-trailer weighing up to 80,000 pounds generates vastly more kinetic energy than a typical 3,000–4,000 pound passenger car.
Greater mass requires significantly more work and distance for the braking system to absorb and stop the vehicle.
2
Account for air brake system delay
Identify that commercial truck air brake systems experience brake lag distance (the time required for compressed air to travel through the brake lines).
Brake lag adds approximately 32 feet of travel distance at 55 mph before the brake pads even contact the drums.
3
Compare total stopping distances
Establish that while a passenger car traveling at 55 mph stops in about 200–240 feet, a fully loaded commercial truck requires nearly 400 feet to stop completely.
Claiming that both vehicles stop in approximately the same distance contradicts physical braking dynamics and DMV safety rules.

Key Concept

Commercial Vehicle Stopping Distance and Braking Dynamics
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Topics

Large Commercial Trucks and No-Zones

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