The biggest difference between your lights and the ones on a car are that car lights have a horizontal cuttoff and so they focus the light onto the ground rather than in a circular pattern which can impare other drivers.

Plus its illegal to operate a directional light on a motor vehicle (like the ones police cars used to have on the A-pillars) as far as I know it most states. Your 1500 lummen helmet light, as you stated, is the rough equivelant of a car headlight,... which you can and have pointed at motorists.

I have some family members who have had eye surgery which produce halos around lights. Driving at night where bright lights are involved produce multiple halos in their vision. Shining a light at them may produce your intended result of them stopping, but it may confuse them as well since they may not be able to pinpoint your location because of the intensity of the light.

You are knowledgeable for sure, dispense your knowlege freely and are open to helping others which is GREAT..... but your delivery often comes off as boastful when you post you lumen output.

For sure, I would like brighter lights, and am a bit envious of your output...... but to put it another way.....

One of my best friends does really well for himself. He has a Lamborghini Gallardo which he bought new.... but when people ask him what he drives, he says a Honda Pilot. (Because he has one of those too). Just becuase he has the Lambo, does not mean he always has to SAY he has it.