"As you can imagine, it's somewhat difficult to get volunteers," Hachikian said. "It's late, and it's cold; it's not exactly the most pleasant task."

But now about 25 volunteers staff Safetywalk. Most of them have volunteered before and about 60 percent are male. Volunteers serve two-hour shifts, toting cell-phones and walkie-talkies funded by the Harvard University Police Department. And Hachikian said volunteers are encouraged to travel by bike to cut down their response time.

"We're highly mobile," Bell said.

Last year, Hachikian said, fewer students called Safetywalk than he thinks should have. Only six to seven people called each week, Bell said, many of them repeat callers.

Once students called once, they found Safetywalk responsive and friendly, Hachikian said.

"One of the ultimate goals this year is to get increased usage," Hachikian said.

This year's co-directors say they have begun a campaign to publicize Safetywalk's services, and the University has pitched in, listing Safetywalk in the pamphlet of Safety Services it distributed to students this fall.

Hachikian and Neumann are also encouraging volunteers to wear Safetywalk T-shirts. In the past week they plastered the Yard with posters and circulated an e-mail informing students of the service.