A £30,000 reward is being offered after two track-side fires in Coventry caused widespread disruption to trains services across the UK this week.
The fires at Canley on Monday disabled all signalling equipment between Coventry and Birmingham, and affected passengers up to Glasgow and down to London, Network Rail said.
The disruption cost the regulator £1.1m in compensation to train companies.
The fires, started deliberately, are a repeat of a similar incident in May.
Network Rail said services between Coventry and Birmingham had to be cancelled on 2 May after two fires were deliberately set, causing signal failures between Canley and Hampton in Arden in Warwickshire.
British Transport Police (BTP) said it had been investigating that incident and was trying to establish if the same person was responsible for the latest arson attack.
"Since the first incident in May, we have been working hard to find the person responsible, including house to house enquiries, CCTV trawls, media appeals and scenes of crime analysis," Det Insp Gareth Davies from BTP said.
"The railway is a dangerous place and whoever is doing this is putting themselves at great risk.
"I'm certain someone out there knows who is behind these attacks and I'd urge them to come forward - not only so we can put a stop to these crimes but also to prevent anyone from being seriously hurt."
Martin Frobisher, route managing director for Network Rail, said the disruption caused "misery" to hundreds of thousands of passengers and urged anyone with information to contact transport police.
Network Rail and Virgin Trains are each offering £15,000 to anyone who provides information that leads to the successful prosecution of those responsible.