As you picture her in that outfit, you begin to squeeze your PC muscle hard once every 5 seconds. If you cant stroke your cock in the traffic, at least you can squeeze your PC muscle, which is between your balls and ass. Then you take a 5 second break before you squeeze it again. You start to squeeze and hold your PC muscle tight for as long as you can before taking your 5 second break. You focus on squeezing your asshole tight, holding it and feeling the sensation in your prostate and cock head.
You keep doing this while you study her body for two minutes straight.
The tip of your cock is pressing hard against your pants now. You can feel the cum building up in your balls.