The number of people residing in campers and other vehicles surged 46 percent over the past year, a recent homeless census in Seattle’s King County, Washington found. The problem is “exploding” in cities with expensive housing markets, including Los Angeles, Portland and San Francisco, according to Governing magazine.

The problem of vehicle residency is national in scope, although its impact may be more “acutely felt in urban areas where space is more limited,” said Sara Rankin, an assistant professor law at Seattle University and the director of Homeless Rights Advocacy Project, in an email to CBS MoneyWatch.

Challenges abound for people who live in their vehicles, ranging from racking up parking tickets to finding a safe place to park and shower, advocates say.