If you have to ride in low light/no light conditions, back and front lights are a must.
You may see cars, but they may not see you or not in time to avoid running all over you .....

I see too many bike riders without light....
And have backups : a red Photon 3 in blinking mode, hanging from a safety pin, on your back is much better than no light at all.
A hand held (or tied to the handlebar with a bit of Velcro) Nuwa? Q3 or a Inova T2, or a head lamp, anyone is usefull when your main front light decide to die on you (replacement bulbs are nice, but I don't trust the light of my bike ... always burning out when I need it ... it doesn't like thehigher voltage when going down a slope a bit too fast...)

In addition, when it's dark, I wear a luminescent jacket (salvaged from an airport maintenance crew ...!!).
So, if I'm run over by a car, I can sue the driver for intention to commit a crime !! He won't be able to say he didn't see me ..... <img src="/images/graemlins/grin.gif" alt="" />