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Difficulty: EasySpeed on Curves and Downgrades

Posted advisory speed signs on roadway curves are calibrated for passenger cars, meaning a commercial vehicle with a high center of gravity may need to travel below the posted advisory speed to prevent rollover.

Answer: Answer

Answer

True: Posted advisory speeds on curve signs are set for passenger cars, requiring commercial vehicles with a high center of gravity to travel below the posted speed to prevent rollover.
The statement is correct because advisory speed plaques posted on curves are engineered around the performance and center of gravity of passenger vehicles. Commercial motor vehicles carry greater mass and higher centers of gravity, requiring drivers to slow down below the posted advisory speed to maintain stability and prevent rollovers.

Step-by-Step Solution

1
Identify the standard vehicle baseline used to determine roadway curve advisory speeds.
Recognized that advisory speed limits are established based on the stability and traction limits of passenger cars.
Traffic engineering standards design curve advisory speed plaques for standard four-wheel passenger vehicles rather than heavy commercial trucks.
2
Analyze how commercial motor vehicle physical characteristics affect curve stability.
Determined that heavy loads and a high center of gravity make commercial trucks far more vulnerable to off-tracking and rollovers during turns.
Centrifugal force acting on a higher center of gravity generates greater tipping moments at equivalent speeds.
3
Evaluate the safety requirement for commercial vehicle curve entry speed.
Concluded that commercial drivers must often negotiate curves at speeds lower than the posted advisory limit.
Reducing speed below the advisory limit ensures the vehicle stays within safe lateral acceleration limits and maintains tire grip.

Key Concept

Curve Advisory Speed Limits and Commercial Vehicle Center of Gravity
Estimated Time:45s
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Topics

Speed on Curves and Downgrades

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