Metro's top rail executive is stepping down.

Dave Kubicek is resigning from his job as deputy general manager for rail operations after six years at the transit agency, according to an internal memo. He was the top aide to General Manager Richard Sarles.

Kubicek, whose resignation is effective March 18, led the agency's push to catch up on track maintenance after years of neglect and the June 2009 Red Line crash, which killed nine people and injured dozens more.

He also engineered the purchase of the new 7000 series rail cars, which are due to arrive next year and will replace Metro's oldest railcars and beef up the system for the new Silver Line.

Sarles praised Kubicek in a memo to employees Wednesday.

"He embraced the need to create a safety culture, maintain and rebuild the rail system and prepare for the arrival of the Silver line," Sarles said. "I personally appreciate the energy and passion he brought to his role on a 7-day a week/24-hour a day basis."

Kubicek's announcement Wednesday came as a surprise to Metro watchers, raising questions of a possible shakeup in the transit agency's top circle. Kubicek has not announced any future plans, Metro said.

Among Kubicek's responsibilities were the safety and maintenance of Metro's rail operations -- which have experienced several nasty and public problems recently.

January's meltdown on the Green Line was a public relations headache for Metro, as hundreds of riders chose to evacuate from dark, hot trains stuck in a tunnel after an employee mistakenly cut power to the tracks. Tuesday's single-tracking on the Orange Line was another potentially unsafe foul-up, as riders had to pack platforms and trains because crews were working furiously to repair a signal that a test train broke overnight.

Metro said Kubicek was leaving because he wanted to move on from the transit agency. He will be temporarily replaced by Rob Troup, assistant general manager of transit infrastructure and engineering services.

"After six successful, hard years of service, Mr. Kubicek had indicated his desire to do something else," Metro spokeswoman Caroline Lukas said in an email.

Lukas said only Kubicek and Sarles "had discussions prior to today's announcement" but that most employees did not expect the resignation.

Metro refused to say how much Kubicek was being paid. The Washington Examiner obtained his pay records under a Freedom of Information Act request in 2011, which showed he earned $260,000 in 2010, including a $30,000 housing stipend. Sarles is making $350,000, according to his contract.