A man who boarded a train in Grimsby vomited all over the windows and seats before urinating under a footbridge at Scunthorpe station.
The offender got on the train at Grimsby Town station with two friends who were all behaving in an anti-social manner between 3.25pm and 4.25pm on Monday, January 8.
British Transport Police investigating the incident said that the man threw up on the seats and windows, and then spat on the windows.
They then left the train at Scunthorpe where the man urinated under the station footbridge and trespassed on the railway by walking along lines from platform 2 to platform 1 to rejoin his friends.
Police believe the man pictured could help with the investigation.
Anyone who knows the man should call BTP on 0800 40 50 40 or text 61016, quoting reference number 316 of January 8.