What is the purpose of separated bicycle lanes, also known as cycle tracks and protected bike lanes?

• To allow cyclists to ride in the middle of the road
• To physically separate bicycles from vehicle traffic for safety
  Explanation:

  "Separated bicycle lanes, also known as cycle tracks and protected bike lanes, physically separate bicycle traffic from vehicular traffic. Bicycle lanes are not intended for pedestrians, who must stay on the sidewalk."
• To provide extra parking space
• To increase the speed of bicycle traffic