I was just in Copenhagen and NOBODY would open a car door without looking out for bikes, since there are more bikes than cars. Bike lanes in the US are just not done right, giving bikes a small space to ride surrounded by cars. Our examples in NYC are horrible. 1st Avenue has a bike lane that puts us in the path of left turning cars, most of which never look. We are unable to avoid obstacles because it is too narrow, we can't be seen because there is a line of parked cars between us and the moving cars. It just doesn't work even though the number of cyclists has exploded over the last few years. Corraled, hidden and marginalized. And the NYC police will ticket cyclists for doing things that drivers would get away with. There was a cop standing at a busy cycling intersection telling us we should have bells, as if bells can be heard inside an air conditioned car, or by a pedestrian with earbuds. Useless. A loud YO works better, and I proved the point as a pedestrian just started walking into the bike lane in front of me against the light, the guy the cops were reminding was right behind me. He heard my shout as I was already wide of him, and the guy behind avoided him.

Anyway, the best defense against being doored is not riding next to them. No light is going to prevent it. That said, GET BRIGHT LIGHTS. Any of the previous suggestions would be fine, or get a dynamo powered light like I have. Just get something bright, don't worry about it being too bright because you can always turn it down.