When and why?
Every weekday in the winter. Commuting to and from work.

Do you have lights? What kind and how many?
Dinotte 800L in the front, Dinotte 140L in the rear, plus a PBSF strapped to the back of my helmet.

Streets? MUPS? Neighborhood? Parkways and busier streets?
Streets and MUPS When commuting. Sinlgetrack on my Mountain Bike. Night riding on singletrack is pretty cool!

Commuting?
Yes

Just for fun?
Yes when Mountain Biking at night.