Boston-area advocacy groups are now alleging in a federal complaint that the MBTA violated civil rights guidelines by not considering the impact on low-income and minority riders when it decided to end its late-night service.

In the complaint filed on Tuesday, three groups – the Conservation Law Foundation, Alternatives for Community and Environment, and the Greater Four Corners Action Coalition – accused the MBTA of using flawed data in its "equity analysis," which is a federally required examination of whether terminating a specific service would affect low-income or minority riders more than the general public, Boston.com reported.

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"This use of overly broad population data allowed the MBTA to conclude that the cancellation of late-night service would have no disparate or disproportionate impact," the complaint was quoted by Boston.com.

Concluding that late-night service was not “cost-effective,” the MBTA’s fiscal control board voted to end the service in February, WCVB reported.

Without late-night service, most of the last trips on the T now take place between midnight and 1 a.m. on a daily basis, according to the transit agency's website

"Some of the T’s most vulnerable customers were affected by the termination of late-night service," Rafael Mares, a vice president with the Conservation Law Foundation, was quoted by the Boston Globe. "The service that’s so important for late-night shift workers has been terminated since March, and nothing else has been put in place."

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Despite the complaint, the Federal Transit Administration told the MBTA that their analysis was "properly documented and has met their requirements," MBTA spokesman Joe Pesaturo said to WCVB.