What does 'reaction time' refer to?

• The time it takes for a vehicle to come to a complete stop
• The time it takes for the brakes to engage after pressing the pedal
• The time it takes a driver to react, think, and hit the brakes after perceiving a need to stop
  Explanation:

  "The time it takes a driver to react, think, and hit the brakes is called reaction time."
• The time it takes for a vehicle to accelerate from a complete stop