Mr. Chaney said that while he looked for work, he did not reveal his situation to his son, who was going to school on a basketball scholarship, because he did not want to become a distraction.

While pride is usually the motivation for not telling friends or family, worries about the law and harassment are more often the reason people give for keeping their situation hidden. Safety is also a concern, experts say, since homeless people are frequently targets for crime and physical abuse.

"A lot of what people do to keep the secret sounds paranoid, and some of it probably is," said Michele Wakin, who wrote her doctoral dissertation about people living in their vehicles in California and who is now a professor of sociology at Bridgewater State College in Massachusetts. "But when you're trying to be discreet and you're spending a lot of time in one area, little things get noticed."

People often develop severe back problems because they resist reclining their seat while sleeping, Ms. Wakin said; if questioned, they want to be able to tell the police that they were just napping. People also build elaborate compartments in their cars to hide bedding, she said.

Mr. Alford said he had learned to move slowly to avoid rocking the car and attracting attention when he was inside. When he has a lot of items to take from his car to the library where he spends much of his time, he makes several trips rather than load his arms and seem like a "bag lady," he said.

"It might seem crazy, but the stakes are pretty high in the suburbs when it comes to staying invisible because it's supposed to be sanitized out here," said Mr. Alford, who works occasionally as a Web developer. "People call 911 in the city to report seeing a homeless person, and the cops laugh. Out here, the cops are out the door in no time when that call comes in."

Experts say there are 2.1 million to 3.5 million homeless people nationally. Ms. Wakin said that the vigilance required to live in a car was one reason there tended to be fewer people who are drug addicted or mentally disabled living in their cars, compared with those living on street grates.