What does a diamond-shaped marking in the center of a traffic lane typically indicate?

• The lane is only for vehicles making a right turn.
• The lane is about to end or merge with another lane.
• The lane is designated for high-occupancy vehicles (HOVs) or other special use.
  Explanation:

  "The lane is designated for high-occupancy vehicles (HOVs) or other special use."
• The lane is reserved for emergency vehicles only.