If you made an LED, of exact shape, position, and LUMEN OUTPUT as a halogen filament, then it could be made 100% DOT legal. But there is no such product I'm aware of.
The reason DOT spec maximum lumen for each halogen bulb, is because a reflector housing for that bulb can only have a max lux (brightness) of scatter light, as well as main beam pattern.
The best housing design still scatter. If you put a 6,000 lumen LED in place of an 1,800 lumen filament, even at the exact position, the scatter would blind people. Projectors have far less scatter, and, within the main beam the lumens is distributed better, so lower lux. That's why you can have a 5000 lm project LED, but not in a reflector housing.
