When one vehicle is towing another by means of a chain, it is typically required by law in many jurisdictions to display a flag or cloth on the towing mechanism (such as a chain) to alert other drivers. The flag should generally be at least 12 inches square and be of a bright color, often red or orange, to increase visibility.
The other options, such as having a red light or vehicle with metal reflectors, may not be universally required but can be good practices for safety. It’s always best to check local traffic laws to understand the specific requirements for towing in your area.