Late-night MBTA service is scheduled to start Friday, and T officials don’t want you to forget it.

Six hundred signs advertising the T’s new weekend extended hours will appear on buses and trains throughout the system by Friday, MBTA spokeswoman Kelly Smith said.

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The one-year pilot program will keep all subway lines, the Silver Line, and the 15 most popular bus routes running until 3 a.m. Friday and Saturday nights, an endeavor that is expected to cost the T $16 to $17 million and will be subsidized in small part by corporations such as the Red Sox, Dunkin’ Donuts, Suffolk Construction Co., and the Boston Globe.