Now that you mention it, a few nights ago I noticed some emergency vehicle lights that were unusually bright. I can see how those might be distracting, especially for folks like my mom who has cataracts and poor night vision. Those flashers don't need to be that bright to be seen, and I don't see how they're useful as to-see lights for emergency response personnel.

Anyway, I wouldn't use white lights on the rear of a bike, even mixed with red. Too easy for an approaching vehicle to confuse a bicycle with a car's reverse lights and misjudge the closing speed. The typical 50-300 lumen red steady/flashers seem plenty bright enough to be seen, even in traffic with distractions.

I've found it more helpful to elevate the rear lights than make 'em brighter. Add red lights to the rear of the helmet, clipped onto a backpack, back of the jacket/jersey, or on a trunk bag. Gives vehicles a better chance of seeing the lights in traffic. During nighttime group rides I've noticed bikes with rear red lights only on the bikes themselves -- on the rear rack or lower -- can't be clearly seen in traffic because some cars physically block the view. But if the cars can see the rider's helmet or torso, they can see a red light mounted higher.