A headlamp system provides for the high beam headlamp filaments to be connected in series across the supply voltage for half voltage energization in daytime running lamp operation when the ignition switch is closed, a DRL enabling switch is open and the headlamp switch is not in a headlamp on condition. In normal high beam headlamp operation, the high beam filaments are connected across the supply voltage in parallel for full voltage energization. The DRL enabling switch may be a park brake switch. The headlamp switch may have a fog lamp energizing condition to energize fog lamps; and the system permits such energization when the headlamps are connected in series but not when they are connected in parallel in normal high beam operation. A circuit is provided to sense when one of the high beam filaments is burned out and latch the daytime running light operation off with a signal to the vehicle operator.