When your high beams are on, a signal from oncoming cars will automatically dim them, preventing night blindness - no more high beam/low beam. Ten seconds after the signal diminishes (and the oncoming car passes by) the high beams come back on.
This can also be used on brake lights for people behind you. If their high beams are on, you tap the brake and their high beams shut down (as long as they are within range of your vehicle).
Reward: Less accidents and aggravation.