For a fish only system, this would probably work fine.
For a reef system, it's not as much about brightness, it's about wavelength and PAR. Needless to say, car tail lights are not designed with the intention of growing corals. LEDs have a very narrow wavelength of light that they produce. You'll need to get the specs on the LEDs used in these tail lights and compare it to existing aquarium lighting to have an idea of whether it will work.
I can tell you that manufacturers who have done this before have spent lots of money on R&D perfecting LED technology that is useful to coral, so it will be a challenge working this out. I'm not saying it's impossible though.