ATLANTA -- When developer Bob Silverman wanted to turn an abandoned lumberyard near a noisy Atlanta rail switchyard into a Provence-style neighborhood four years ago, it wasn't just bankers who snickered. The trend also reflects the appeal of living downtown, where people choose to be surrounded by a diverse population and close to mass transit. Neighborhoods' close quarters help incoming residents to feel safe and comfortable, proponents say. "Nobody wants to be a pioneer in an industrial neighborhood if you're all alone," says Delores Conway, director of the Casden Real Estate Economic Forecast in Los Angeles. But the biggest reasons for converting the ugliest lots into thriving neighborhoods are that new residents can avoid traffic hassles and cut gasoline costs. American households spend 20 percent of their household budget on transportation, according to the Urban Land Institute. People can afford to live in more expensive urban enclaves if they live closer to work or trains. That is essentially the European model, where households spend only about 7 percent of their budget on transportation, according to the Institute.