The UK term for the US "low beam" is "dipped beam". Many US vehicle lighting systems switch to a lower wattage beam when the "dimmer" switch is operated, whereas the Europeans actually change to a filament that's in a different place in the bulb, resulting in the beam actually being focused at a lower angle rather than set to a lower intensity.
On my first car, a 1938 Austin Seven, it was a mechanism to wonder at. In the back of the driver's side headlight, there was a solenoid which physically moved the headlight's reflector to redirect the beam towards the sidewalk and away from approaching traffic. At the same time, a switch built into the system turned the other headlight off.
On a wimpy 6-volt system, I'm amazed anyone thought such mechanisms were necessary. I figured that at any speed above 45 mph, the wind would have blown the lights out anyway.
I did do a "modern" (early 1960s) conversion to double-dipper headlights. I think they were 48-watts, a hell of a load for a 1930s 6-volt generator. After carefully aligning both lights on high beam, I ventured out in the dark a few days later. When I hit the dip-switch, one light went down and the other one started looking for German bombers.