The proposed no-fare program would begin in five cities, as Germany endeavors to meet EU air pollution targets. But similar plans haven't always worked as hoped.
Dozens of ballot measures to raise local taxes were approved, and President-elect Donald Trump has called for more spending on infrastructure. But there are questions about Trump's funding sources.
In a number of cities, what riders say may be recorded. Transit agencies are adding audio recording for security reasons, but civil liberties advocates say it's an invasion of privacy.
New York City plans to add streetcars to connect its isolated areas, but critics are wary. Streetcars in other cities have few riders, and Washington, D.C.'s streetcar opening was delayed for years.