Final answer:
Passenger vehicles, trucks, and certain buses are mandated to have headrests to enhance safety during impacts.
Explanation:
According to Federal Motor Vehicle Safety Standard $571.202 subpart B, all passenger vehicles, trucks, and certain buses are required to have headrests or head restraints. Headrests play a crucial role in providing a normal force on the head during impacts, maintaining a safe position for the neck. This is a vital safety feature mandated to enhance crash protection and reduce injuries.
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