full beam 
noun [mass noun] British
The brightest setting of a vehicle’s headlights: his headlights were on full beam...
- The silver Mini Cooper drove smoothly down the darkened tunnel with its full beam headlights on at 30 mph.
- The reasoning here being that I would see the full beam headlights of any other vehicles in the distance and have plenty of time to slow down.
- He told the court a car came round a bend with full beam headlights on which blinded him, and within a second, a dark object fell into the side of his car.