I go [almost] as fast as I can [almost] all the time. I can go faster when there is a [roadie-ish] cyclist in front of me, or one behind me that I recently passed . I realize they are not out there to race me, but that doesn't negate the motivation that they unwittingly offer. I certainly bear no ill will to roadies, God love 'em. Stale green, as well as amber lights are a big motivator also. I get my best workouts when there is a big headwind that just completely pi$$es me off.
This has been a very entertaining thread. : Rock-on, OP!

[disclaimer] I fully realize, any "roadies" that I've kept pace with, or passed, were either not competitive racers, or if they were, were not "trying".