I'd make an effort not to blatantly stare at your crotch but I wouldn't be able to stop sneeking glances at your huge bulge. Then I'd jerk off later thinking about it
I'd stop whatever it is I was about to do, wait for that bus there with you, then make sure I'm seated next to you on that bus even if it's empty, then...well, you know what I'll be 'up' to! ;@)