Come off it! They have to meet legal requirements, a red rear light will not be drowned out by white headlights, and if the road is that busy, there'll be so many headlights the cyclist will be lit up like Broadway.
The legal requirements, though, are feeble. A minimum of four candela for a flashing light - most flashing bike lights are rated in lumens, and they're typically in the 25-30 range which is about half the requirement. UK cycling recommends fitting two, but light doesn't necessarily work geometrically, so putting 2 25 lumen lights doesn't give you 50 lumens.
Steady lights have to comply with BS 6102/3, but the requirements of that are pretty feeble, too; coupled with that, most manufacturers of bike lights are producing units that are marked as compliant with BS 6102 - you can have as many lights as you'd like, but at least one of them has to conform, so it's on you as the rider to check, not on them to ensure that all their lights are compliant.
It's also worth noting that the lights are required to be fitted no more than 1500mm from the floor, so all those adults with lights only on their helmets are probably in breach of the requirements.
Also worth noting that bikes (between sunset and sunrise, at least) are required to have amber reflectors in the front and back of the pedals - most of the racing bikes I see out there have the cleated pedals which rarely include these.
O.