A female Bradford bus passenger was caused alarm and distress when a male passenger outraged public decency.
Police are now appealing for witnesses to the incident on the 626 bus travelling from Bradford centre to West Bowling on June 12, between 5.30-6pm.
The man boarded at the stop at Market Street, outside the Ginger Goose public house.
He initially sat a few rows in front of her before moving next to her at the back of the bus and then allegedly outraged public decency.
A man officers want to speak to in connection with the indecent is described as Asian, in his early 20s, with shaved hair at the sides which was gelled or greasy on top.
He was wearing black jogging bottoms, a black running jacket and had a black Samsung Galaxy S mobile telephone.
PC Josh Hirst of the Bradford East Neighbourhood Policing Team, said:“I would appeal to anyone who witnessed this incident to get in contact on 101.”