The cyclists on Beacon St / Hampshire St. between Porter Square and Kendall tend to be fairly well behaved, if only because the cops have been known to set up cyclist ticket traps on that stretch. (Yes, really!)

I confess that I have made that mistake on JFK myself -- I don't drive it often, and while there may be signs I didn't notice until the last block that the left lane is a left-turn-only lane. My bad. I will hit myself with an honorary BBC foam bat in penance!