Lights on ALL the time no matter what on the street, even for short rides to a buddy's house. On the bike path I turn on the front at night, and during the day at crowded sections of the path. For me the rear light seems like a waste of battery on the path as I usually only get passed by kited up racers/commuters and closing speeds are nowhere near what you get on the street with cars. (Always on flash unless otherwise needed for my own visibility, but with the streets I ride being seen is the higher priority as they are well lit enough for me to see where I am going most of the time)