DRIVING ON UNFAMILIAR RURAL DIRT ROAD AT NIGHT, SWITCHED TO HIGH BEAM TO SEE UPCOMING INTERSECTION AND ALL HEADLIGHTS WENT OUT. STUNNED, I LOST SEVERAL CRITICAL SECONDS BEFORE I RESTORED THE LOW BEAMS AND LOCKED UP THE BRAKES. TOO LATE. UNABLE TO TURN SAFELY, I LEFT ROAD, WENT DOWN EMBANKMENT THROUGH FENCE BEFORE STOPPING IN PASTURE. SUBSTANTIAL FRONT END AND BODY DAMAGE TO TRUCK.