As a young lad, I often took the train into London, and would sit opposite an attractive woman when possible...I would soon get a bulging outline along my thigh under my jeans or trousers, and loved seeing the reaction...some ignored it, but a surprising number would 'discreetly' gaze down directly at it! When I noticed them glancing, I would deliberately tense it, making my stiff young shaft twitch and move.....I saw quite a few nipples getting erect under blouses and tops, and it seemed to be the more mature woman who enjoyed what they saw!