Raj Rajkumar, director of Carnegie Mellon University’s Mobility21 research center, which focuses on transportation issues, said studies have shown that mass transit reduces congestion and pollution. But he also said there is some truth in concerns that transit could bring gentrification.
To offset that, he said, transit plans should be paired with measures to increase affordable housing.

Still, in most places and over the long run, buses and trains are the most effective and cleanest way of moving large numbers of people large distances, he said. Ride-sharing can help people on shorter trips, Mr. Rajkumar said, or getting to and from a train station. “But if you’re going 30 miles, Uber is less suitable. I don’t think Uber and Lyft can really replace public transit,” he said.
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