So, I took the plunge and bought the L&M ARC HID light. It's overkill for the tunnels--my original reason for getting a light. Having done a lot of reading and thinking about night riding, however, I decided to outfit myself with something that would allow me to do it properly (I also bought a mack daddy Cat Eye taillight). It could end up being a really expensive experiment or the best money I've spent on my bike.

Ironically, I went for a ride on Monday that despite being theoretically in the daylight, it was really hard to see. I would have benefitted from some lights even in those conditions.

Thanks for all the great advice.

Kate