A crew of about 50 volunteers interested in seeking out and helping the homeless recently descended on District neighborhoods—-not unusual in a city known for both its thriving political culture and underclass. But the do-gooders who wandered the streets between 12 and 6 a.m. didn’t hand out plastic-wrapped ham sandwiches and bottles of water. Nope, all these volunteers had to offer were three pages of semi-invasive questions.

It’s part of the opening salvo of Mayor Adrian Fenty’s Housing First program, which “turns the traditional approach to providing homeless services on its head,” according to the Web site of Ward 6 Councilmember Tommy Wells, who supports the effort. The idea is to find the most needy and troubled citizens and get them right into city-provided shelter. To that end, the D.C. Department of Health and Human Services has begun acquiring housing vouchers so that it can shelter 400 of the most vulnerable members of D.C.s homeless population by the fall. The digs doled out will be permanent and scattered throughout the city, as opposed to traditional warehousing strategies.

But how does the city discover who the most vulnerable are? By hitting the streets in the wee hours, when the homeless—-and perhaps drunk people—-are the only ones out and about. After rousting potential clients from their sleep, volunteers asked them questions that feed into a vulnerability index developed by based on the research of homelessness expert Dr. Dennis P. Culhane. The index rates a person’s vulnerability by looking at things like the length of time an individual has remained homeless and the individual’s history of cold-weather injuries.

Adam Maier, director of the Ward 6 Committee on Human Services, joined up with volunteers conducting interviews on a Tuesday night in the Union Station area. (He blogs about the experience here.) Over the phone, Maier says the process went smoothly: “I was very surprised at how I didn’t get turned away; the whole night there was only one person who was distrustful,” he says.

Maier adds that every person interviewed, whether they responded to any questions or not, received a five-dollar McDonald’s gift card. —-Rend Smith

CORRECTION: Due to errors by reporter Rend Smith, an earlier version of this post misstated the name of D.C.’s Department of Human Services and said that Dr. Dennis Culhane developed the vulnerability index used by the department. In fact, the department’s vulnerability index is based on Culhane’s research.