Police have described an attack on a train in which a bag was filled with stones and faeces and then suspended across a railway line as "abhorrent".
British Transport Police said the bag was suspended from a cord which had been stretched across the railway line near Driffield, East Yorkshire, on Saturday, July 23, shortly before 8pm.
Pc Gary Shepherd said: "A length of green cord was attached to the signal gantry and stretched across two sets of railway lines then attached to a tree on the opposite side. A plastic bag containing ballast and faeces was then suspended from the cord at train window height.
"The 17.41 Sheffield to Scarborough service, which was travelling through the area, struck the suspended bag at around 50mph, narrowly missing the driver's windscreen. A small dent was made to the front of the train, which was also covered in faeces."
Pc Shepherd added: "This is absolutely abhorrent behaviour. Fortunately no-one was injured, but as you can imagine the driver was extremely shocked.
"The train had to be taken out of service to be cleaned. I have no idea what would possess someone to do such a disgraceful thing. A lot of planning must have gone into this, setting up the cord and attaching the bag would have taken some time.
"Unfortunately during the holidays we see an increase in offences on the rail network. The railway is such a dangerous environment, trains cannot stop quickly or swerve, and are often not seen or heard until it is too late. Trains travelling at top speed can take the length of 20 football pitches to come to a complete stop.
"The area where this incident took place is a remote location over the River Hull but I would like to appeal to anyone who may have seen anyone hanging about the area on Saturday night to contact us."
Officers are now stepping up patrols in the area and would ask for anyone with information about this incident to come forward.