Riding at night = fun.
However, I did a dual line paceline on Monday night with an unfamiliar group of about 40 on an unfamiliar route that had my full attention. I couldn't tell you exactly how fast we were going as I couldn't see my Cateye, but I'd guess in the 19- 21 mph range most of the time. Not so fast in the daytime but scary fast in the pitch black night on a Chicago Forest Preserve road 18" behind one stranger, rubbing elbows with another, and who knows what's going on in the gap behind. Lights were kind of a problem in fact because I felt blinded by some of the red blinkies - more incentive to keep the gap so close that it's out of my range of vision I guess.