Aging Transit Systems Grapple With Repair Backlog Driven by high gas prices and an uncertain economy, Americans are turning to trains and buses to get around in greater numbers than ever before. But the aging transit systems they're riding face an $80 billion maintenance backlog that jeopardizes service just when it's most in demand. The boost in ridership comes as pain at the gas pump and the sluggish economic recovery combine with a migration of young adults to cities and new technology that makes transit faster and friendlier than in the past. The number of transit trips over a 12-month period will likely set a new record later this month or next, say Federal Transit Administration officials. The current peak is 10.3 billion trips over a year, set in December 2008. But decades of deferred repairs and modernization projects also have many transit agencies scrambling to keep trains and buses in operation. The transit administration estimated in 2010 that it would take $78 billion to get transit systems into shape, and officials say the backlog has grown since then. In some places, workers search the Internet for spare parts that are no longer manufactured. In others, trains operate using equipment designed, literally, in the horse-and-buggy era. In this photo taken, Wednesday, Aril 11, 2012, Federal Transit Administrator Peter Rogoff, right, and Bay Area Rapid Transit (BART) General Manager Grace Crunican walk through a work area during a tour of the BART Maintenance Yard in Hayward, Calif. The aging trains and buses they're riding, however, face an $80 billion maintenance backlog that jeopardizes service just when it's most in demand. In Philadelphia, for example, commuters ride trains over rusty steel bridges, some of them dating back to the 19th century. The Southeastern Pennsylvania Transportation Authority - which operates subway, trolley, bus and commuter rail systems - is responsible for 346 bridges that are on average 80 years old. Officials said they may be forced to slow trains or even stop them from crossing one bridge that's 1,000 feet long and 90 feet above the ground if it deteriorates further, leaving stations on the other side without service. A key power substation relies on electrical equipment manufactured in 1926. There's no hope for acquiring spare parts, so workers try to open the boxes housing the equipment as infrequently as possible to prevent damage from exposure to the environment. "We're operating on a prayer on that line," Joseph Casey, the transportation authority's general manager, said in an interview. If that fails, half of our commuter rail system would shut down. The system carries 125,000 passengers on weekdays. The transportation authority doesn't have enough money to replace the bridges or outdated electrical equipment, Casey said. In recent years, the authority has spent $600 million on renovating elevated portions of a subway line that dates back to 1905, and $100 million to install a federally required rail safety system. Another $327 million was spent on new rail cars to replace 72 cars built in 1964. Some of the older cars - nearly 40 of which are still in service - are in such disrepair that passengers get soaked from leaks when it rains. And yet passengers made 34 million trips on the transit system last year, the most in 22 years, despite a 9 percent fare hike. So far this year, ridership is up 3 percent, Casey said. San Francisco's subway system, Bay Area Rapid Transit, faces many similar problems. Opened in 1972, BART was at that time the most automated subway system in the nation. But circuit boards and other electronic components for 449 original train cars - out of the system's total of 669 cars - are now 40 years old, no longer manufactured and often impossible to replace.