PHAT stands for Protect Your Head at All Times, Protect Your Head on All Terrain.

It is a team of volunteer doctors and safety professionals led by Robert Williams, M.D., doctor to the Smugglers' Notch Ski Patrol and associate professor at the University of Vermont College of Medicine.

Williams said snowboards and super-sidecut skis have driven a dramatic change in what skiers and riders do on the mountain, and that resorts have responded by offering a variety of terrain and experiences.

"Skiers and riders have to adapt by skiing and riding responsibly and wearing helmets," he said.

He said glades, terrain parks, and off-piste skiing have led to a decrease in the speed that people ski and ride, meaning that many accidents are at slower speeds, where helmets can be most effective.

At the same time, he said, the surfaces that skiers or riders hit are often very hard and unforgiving, like the icy walls of half-pipes, or trees in the woods.

"In terrain parks, at the top of an arc the skier or rider actually achieves zero velocity. But when they fall, they're falling against really hard surfaces.

"Backcountry skiers and riders are a long way and a long time from help, so wearing a helmet to reduce the severity of an injury really makes sense. They can save a concussion; if you have a head injury but no concussion, that's good. If you have a head injury with a concussion, but not worse trauma on top of that, that's good," he said.

PHAT is based at Smugglers' Notch Resort but visits ski resorts across New England throughout the winter. Upcoming stops are Feb. 22 at Sugarbush and Feb. 24 at Okemo.

The stops include information sessions by PHAT and promotional safety offers by the resorts.