VANDALS have caused well over £250,000 in damage to buses in Huddersfield and Calderdale over the last year.
In some of the worst attacks, vandals have etched the initials NV on bus windows and then used paint sprays to daub them on vehicles.
Now, police and bus chiefs have joined forces to find the culprits.
People have been urged to name those responsible - and they could earn a cash reward of up to £500 from Crimestoppers .
Nigel Winter, First Calder- dale's commercial director, said: "We are appealing to people to pass on information about vandalism on buses.
"Anyone who recognises the NV tag should call Crimestoppers. There are high rewards available for information leading to the arrest and charge of graffiti offenders.
"All calls to Crimestoppers are confidential."
Mr Winter added: "About £250,000 of bus glass has been damaged by etching, with graffiti incurring further costs to remove."
He said it takes a day to repaint the back of a bus to get rid of the unsightly graffiti.
"A day's labour, the materials, the loss of revenue from the bus being off the route. It all adds up," said Mr Winter.
"We think the graffiti is being done at bus stations or quiet terminuses."
Crimestoppers regional co-ordinator Det Sgt Ian Froggett said: "This is a despicable and selfish act. What the perpetrators of this graffiti don't seem to acknowledge is that it is criminal damage and they could receive a prison sentence.
"Buses have to be taken out of service and services may be disrupted. All this has to be reflected in bus fares.
"The public can help to prevent this. Somebody must know who is causing this damage and be prepared to make a phone call to Crimestoppers."
Calls to Crimestoppers on 0800 555111 are not taped, they are not traced and callers are not asked to identify themselves. They don't even appear on itemised billing.
There are cash rewards on offer of up to £500 for information leading to an arrest.