Lights

Almost certainly. The question is how fast can you go, and what is it like when cars are coming the other way? I have often ridden unlit roads with just a cateye el-510 on low - far dimmer than the fenix. I close my left eye when there is a car coming so i will still have one dark-adapted eye when they have gone, and i sometimes take a second el-510 which i turn on at full power just to descend quicker. The brighter your lights are, the less you can see outside their beam.

thats cllever. gonna remember that