Overhead copper cables on a stretch of the Tyne and Wear Metro are being replaced to deter thieves.
Network Rail said copper cable thefts between Fellgate and South Hylton cost more than £60,000 last year.
The company has not disclosed the material being used instead of copper.
Richard Lungmuss, route director for Network Rail, said: "The theft of cable is a constant drain on our resources and cause of considerable disruption to rail services."
"We will continue to do all we can to deter thieves and to bring those responsible to justice."
Network Rail is offering rewards of up to £1,000 for those who give information which leads to the arrest and conviction of cable thieves.
Det Insp Brian Buddo, of British Transport Police, said: "We have recently arrested and charged nine people in connection with the theft of overhead line equipment in the Sunderland area.
"Those who steal cable are not just risking a prison sentence, they are also risking serious injury and even their lives."
It is not yet known when the project will be completed.