A packed Baltimore trolley illustrates the ups and downs of US public transit

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Nicholas Dagen Bloom, Hunter College

(THE CONVERSATION) Since the 1940s, there has been a broad shift away from public transit across the U.S., and service has declined in many cities, including New York, Boston, Denver, Orlando and St. Louis. A look back at the last national mass transit boom helps explain the challenges that confront modern transit agencies.

Starting in the 19th century, transit companies worked closely with real estate developers to develop “streetcar suburbs” for a growing population. The companies kept fares low, thanks to corporate consolidation, government regulation and thrifty management.

During World War II, producing weapons and supplies for troops fighting abroad became the nation’s top priority. Gasoline, tires and autos were strictly rationed, so most commuters had few ways to get to work other than public transit.

In Baltimore, for example, people could ride a streetcar anywhere in the...