A woman was walking through the Trafalgar Street underpass in Brighton around 1.00am on Monday 30 May.
She was hit on the head with a glass bottle as she walked down the street.
At Brighton station, the bottle had been thrown from the bridge above.
The victim, a 24-year-old woman, needed hospital treatment for a head laceration.
Anyone with information should contact BTP by texting 61016 or calling 0800 40 50 50 and quoting reference 29 of 30 May.
You can also call Crimestoppers anonymously at 0800 555 111.
