At around 11:30am on the 26th of July, a woman was travelling on a tram replacement bus service near Waddon Marsh.
As the woman was preparing to leave the bus she was sexually assaulted by a man.
Officers believe the man in the image may have information which could help their investigation.
Anyone who recognises him is asked to contact British Transport Police by texting 61016 or by calling 0800 40 50 40, quoting reference 249 of 26 July.
You can also contact Crimestoppers anonymously on 0800 555 111.
