An oft mentioned item on many of the blogs I read is the joy and difficulty in riding in a skirt. Dottie and Trisha have offered some suggestions to keep one properly covered, as well as making reference to Sigrid's fig leaf concept.
During the winter, I made a pair of pantalettes out of rayon lining fabric to wear between my wool tights and trousers on the days I would walk to work. The layers would keep me warm, and would resist the friction that would occur between the tights and pants.
This spring, I started to wear the pantalettes under skirts, as they are much better in my windy city than a petticoat (as my dad calls it) or slip. And since I will be a tomboy to my dying day, I find I can still climb trees, fences and lately, ladders into the nose of antique aircraft without worrying that I may be shocking someone.
The transition to bicycle was easy and now I don't worry about what my skirt might be doing as I watch for traffic around me.
I made a second pair for my lighter coloured summer skirts, and decided they should be called cyclettes. Just because.