What does this sign indicate?

• Drivers must stop before the intersection and cannot proceed.
• Drivers can block the intersection if traffic is heavy.
• Drivers must not enter the intersection if they cannot get all the way through without stopping.
  Explanation:

  "This sign indicates that drivers must not enter the intersection if they cannot get all the way through without stopping. This sign is a warning to prevent blocking the intersection and causing traffic jams."
• The intersection is closed to all traffic.