Flashing headlights is when a driver briefly turns on the high beam lights from low beam or no lights at all. This brief flash is use to communicate with other drivers (generally asking for a pass) on the road. Though it can also be used as a type of aggressive driving. Though there is no specific offense of flashing lights, it is a basic breach of road ethics. It can blind other motorists on roads or misguide when used unnecessarily.
It can be used as a warning signal to other vehicles to slow down or acknowledge the presence of other vehicles approaching. It is a clear and obvious signal and hence should be acted upon quickly to avoid any mishap. Flashing lights are a common mode of communication in night driving, as well as on drive in hills and valleys or limited visibility driving. Drivers usually signal other approaching vehicles with flashing lights on sharp bends or narrow roads to allow them to pass and avoid collision. However, high beam lights blind the approaching driver temporarily during limited visibility and can prove hazardous. One must ensure that it is brief. The direction of the high beam lights should be managed well as a driver, to avoid blinding other drivers on the roads. Use hazard lights when necessary to avoid use of high beams when they can be avoided. You can use your fog lights when the weather conditions are foggy.
Driving on the roads is a test for ethics, if a driver is trying to be pushy or move out in front of you, safely slow down and provide room for the vehicle to continue. The pattern of your drive says a lot about the driver. Look out and be alert.