The Beaver County borough of Rochester will showcase two transportation innovations and attempt to unsnarl its busiest intersection over the coming year with construction of a $1.8 million roundabout.

In addition to improving flow at a pinch point where three major roads converge to form a five-point intersection, the roundabout is seen as the centerpiece of a planned transit-oriented development that officials hope will revitalize the borough's struggling business district.

The roundabout, a modern version of the traffic circle, is an innovation that is gaining popularity across the United States but has been slow to take root in Western Pennsylvania. Proponents say roundabouts improve traffic flow, are friendlier to bicyclists and pedestrians and reduce crashes.

"We've always wanted to be out in front of the curve," said Richard Ober, chairman of the Beaver County Transit Authority board. The authority last month got one of the first Smart Transportation grants awarded by the Pennsylvania Department of Transportation to pay for construction of the roundabout.

"We're trying to get the infrastructure together to get ready for development, particularly residential development," said Mary Jo Morandini, the authority's general manager.

Rochester has experienced the same fate as other Western Pennsylvania mill towns, with declining population and a vacancy rate approaching 50 percent in its business district.

The borough's nucleus is where Brighton Avenue, the main drag, intersects Adams Street and Rhode Island Avenue, and drivers queue up for long waits at traffic lights. Mr. Ober calls it "the most congested intersection in Western Pennsylvania."

The roundabout will do away with the signals and create an oval around which traffic would flow continuously. Motorists entering the roundabout will yield to vehicles already in the oval.

"In a year this is going to look so different here," Ms. Morandini said, gazing at the tangle of traffic lights, overhead wires and road signs that will be replaced by a verdant, landscaped island by fall 2010.

Adjacent to the intersection is the transit authority's hub, Rochester Transportation Center, where virtually all of the system's routes converge.

Ms. Morandini said the authority expects to save $25,000 a year in operating costs from improved traffic flow at the roundabout.

The transit system, which serves several county towns and Downtown Pittsburgh, has experienced phenomenal growth, from 473,000 riders in 2002-03 to a projected 838,000 in the current fiscal year.

With many of those riders boarding or transferring at Rochester, the authority is hoping some of that growth will spill into surrounding blocks, where mixed-use retail and housing development is planned on parcels with spectacular views of the Ohio River.

"This is going to take a long time," Ms. Morandini said. "We're not kidding ourselves."

According to the Insurance Institute for Highway Safety, modern roundabouts were developed in the United Kingdom in the 1960s and are widely used throughout Europe.

The first of about 1,000 roundabouts to be built in the United States appeared in Nevada in 1990, according to the institute. It said 23 states have active programs to develop them.

Roundabouts improve safety because vehicles travel in the same direction at slow or moderate speeds, reducing or eliminating the danger of head-on or right-angle crashes. With no traffic lights, drivers don't speed up to make a green light or make abrupt stops on a red signal.

According to the Pennsylvania Department of Transportation, roundabouts bring a 90 percent reduction in fatal crashes and a 75 percent reduction in crashes with injuries.

At the same time, they carry about 30 percent more vehicles in peak traffic than signalized intersections, PennDOT reported.

The state has adopted a policy requiring developers to look at roundabouts as an option when applying for highway occupancy permits, said Colleen M. Brown, the state's roundabout coordinator.

As of last summer there were nine of them in the state, mostly in the southeastern part, she said. One was added as part of a road relocation project at Saint Vincent College in Latrobe last year, and two were built in Cranberry in connection with the new Westinghouse office complex.

"They're becoming really popular throughout the country," she said.

The insurance institute noted that motorists typically are opposed to construction of roundabouts.

"However, opinions quickly change when drivers become familiar" with them, it said.

A 2002 survey in three towns where roundabouts replaced intersections with stop signs found 31 percent in favor before construction, and 63 percent shortly after completion.