Shared centre lanes are used for

• rush-hour travel.
• making left turns.
  Explanation:

  "A shared centre lane (also known as a two-way left-turn lane) allows vehicles travelling in either direction to turn left. Use this lane with caution because vehicles travelling in the opposite direction may also be using it. Never use this lane for through driving or passing."
• regular driving when your way is clear.
• passing other vehicles.