A LONE ROLLERBLADER enjoys a pleasant day under the canopy on the Farmington Valley Greenway in Farmington. (PATRICK RAYCRAFT)

On a late Sunday afternoon in mid-August, five teenagers in shorts press their backs against the outer railing of the Farmington Valley Greenway bridge in the Collinsville section of Canton.

Two bicyclists try to warn the boy in the center against it, but he glances furtively left and right and then jumps. He lands with a resounding splash, followed by a burst of obscenities about the coldness of the water.

The bicyclists shake their heads and pedal away as the four remaining boys debate whether they'll jump, too.

It's the sort of scene that critics cite when they claim Rails to Trails projects like the Greenway invite trouble.

Over the years, groups of homeowners along various segments of the 22-mile route have raised fears of vandalism, trespassing, loitering, litter and noise after learning that the abandoned rail bed near their homes will be converted to a pedestrian and bicycle path.

Such opposition is not confined to Connecticut. After learning about a new Rails to Trails project, neighbors of retired rail lines in some states have strung fences across the route, sued to claim ownership of the land, and reportedly even set fire to wooden ties on the old bridges.

But overwhelmingly, such fears ease soon after a trail is actually built.

``Developers in various parts of the country are building spurs to reach established rail trails,'' said Craig Della Penna, New England field representative for the national Rails to Trails Conservancy.

The organization refers to a half-dozen studies in California, Iowa, Minnesota and Washington that conclude rail trails don't create crime; if anything, they diminish it.

In Connecticut, independent sources back this up. Police in Farmington and Canton, along with state troopers in Burlington and East Granby, all say the Farmington Valley Greenway and its Canton spur have not brought trouble.

``The rail trail has had a real positive impact in Collinsville. We've had absolutely no problems, none,'' said Sgt. Ken Ripley, a 30-year veteran of the Canton Police Department.

Teens very rarely use the trail's Collinsville bridge for jumping, he said. That problem was more frequent when it was a rusting, ignored hulk.

``When they put in the trail along the river, some of the older fishermen said it would be full of kids hanging out. Some people in town were afraid,'' recalled John Marona, owner of the Quiet Sports shop in Collinsville. ``But it never happened. People use it all the time, so kids aren't going to get in trouble there -- they're too afraid of getting caught.''

The Farmington Valley Trails Council is used to hearing opposition as the trail reaches new sections of its ultimate, 22-mile, Suffield-to-Farmington route, and as work progresses on its 8-mile Farmington-to-Canton spur.

``At first, people along the trail put up fences in their backyards to screen it. Then, after a while, you see them cutting doorways into the fence so they can go out on the trail themselves. Then sometimes they take the whole fence down,'' said Stephen Noble, treasurer of the council.

Elizabeth Dolphin, assistant planning director in Farmington, said, ``When they hear it's coming, sometimes people screech. But when it opens, they love it. A lot of the trespassing problems disappear after the trail goes in. The ATVs that race up and down the old rail bed disappear.''

Metal barricades keep motorized vehicles off the path. Police, however, can unlock and lower them to get access in an emergency.

Thieves occasionally break into cars parked near the trail and steal what they can -- cash, wallets, watches, CD players -- in the kind of thing police call a crime of opportunity. But crime on the Greenway itself is extremely rare.

A streaker was arrested there earlier this year. But the rumor of the attempted abduction of a young woman jogger last year near Red Oak Hill Road in Farmington turned out to be just that -- a rumor. Even so, it had to be quelled by a public meeting with police.