What should drivers do when they see this road sign?

• Increase their speed to quickly pass through the corridor.
• Turn on their headlights and drive cautiously for the next 7 miles.
  Explanation:

  "When drivers see this road sign, they must turn on their headlights and drive cautiously for the next 7 miles."
• Prepare to pay a toll in the next 7 miles.
• Expect a mandatory rest stop within the next 7 miles.