The Mount Vernon Bike Trail, where hundreds of bicyclists have gotten flat tires because someone spread carpet tacks on the path, has been less dangerous in recent weeks. But the tack attacks are not forgotten.

In May, one or more vandals wreaked havoc on bike tires by spreading tiny, almost invisible tacks on the path about twice a week. Early June showed some improvement, say U.S. Park Police officials and others who monitor the popular trail. But new tacks found their way into several tires late last month, and police remain vigilant.

"We haven't had one {an attack} in a couple of weeks. Maybe the heat's helped us out," said Maj. Robert Hines, of the U.S. Park Police. That agency has primary responsibility for policing the 19-mile path that runs along the Potomac River from Rosslyn to the Mount Vernon mansion.

Hines said increased patrols likely have deterred would-be tack spreaders, and the use of powerful magnets has eliminated the offending tacks soon after they are reported to authorities. Hines added that no arrest has been made in the attacks.

Among the victims of the vandalism was Tipper Gore, the vice president's wife, who had a flat in northern Old Town Alexandria. In addition, one man was injured so badly in a tack-related tire blowout that he needed surgery and now has a metal plate in his hand.

The incidents have focused attention on the bike path, which on a sunny afternoon has thousands of bicyclists, walkers, runners and roller-bladers. There have been tensions among the various users of the trail, leading to speculation that someone with a grudge against bike riders has been spreading the tacks.