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By Joan Lowy, May 21, 2015, Associated Press

WASHINGTON (AP) — Senate Democrats on Thursday demanded that Republicans provide more money for Amtrak so the railroad can tackle a $21 billion maintenance and repair backlog, including replacing tunnels more than a century old.

Democrats at a news conference cited last week's deadly crash in Philadelphia and said the backlog is compromising safety and service.

Investigators have said the crash could have been prevented if expensive safety technology called positive train control had been in operation. The technology can prevent derailments due to excessive speed and collisions between trains. Amtrak says the system will be ready by year's end throughout the Northeast Corridor, which stretches from Boston to Washington, with the exception of some track owned by commuter railroads in New York.

Democrats want Congress to give Amtrak the entire $2 billion in subsidies the railroad requested for the budget year that starts Oct. 1. They say GOP lawmakers have starved the railroad financially for years.

A Republican-controlled House panel approved a spending bill the day after the crash that provides Amtrak with $1.1 billion, a cut of $251 million from this year.

A spokesman for Senate Majority Leader Mitch McConnell, R-Ky., didn't immediately respond to a request for comment.