If your car breaks down on a highway at night, you should do which of the following?

When your car breaks down on a highway at night, visibility and signaling your situation to other drivers becomes crucial for your safety. Raising the hood of your car and tying a white handkerchief to the left door handle serve as visual signals to indicate that your vehicle is experiencing trouble; the white cloth is universally recognized as a sign of distress or need for assistance.

Additionally, switching on your parking lights enhances your vehicle's visibility to other motorists, making it easier for them to see you from a distance. This combination of actions—utilizing both the visual signal from the raised hood and handkerchief and the emergency indication from the parking lights—provides the best chance of ensuring that drivers can see and respond appropriately to your situation. By taking both measures, you enhance your safety and decrease the risk of further incidents on the road, signaling to others that help may be needed.