In San Francisco, city officials checking on people in the month after busing them out of town found that while many had found a place to live, others were unreachable, missing, in jail or had already returned to homelessness. Within a year, the city found that one out of every eight bus ticket recipients had returned and sought services in San Francisco once again.

In Portland, Ore., a city that has spent three years sending hundreds of its homeless residents around the country, the numbers were worse. Officials found that three months after the departures, nearly half of those transported who could be reached had lost their promised housing.

“That’s a pretty high failure rate,” said Nan Roman, who leads the National Alliance to End Homelessness. “If we were housing people, I don’t think saying 50 percent of them returned to homelessness after a housing intervention would be acceptable.”

Busing programs have been a staple response to homelessness for years, but in the past, Ms. Roman said, some cities seemed to use them as a way to export their troubles.

The newer programs, she said, are designed to provide homeless people a critical path to stability by linking them with familiar support systems. But she said cities may need to do a better job of screening what is realistically waiting at a new destination and to hand travelers off to services near their new homes.