The first roundabout in Jefferson County will keep motorists moving when the J Street expansion gets under way early next year.
The five-way intersection will be situated where J Street meets S.E. City View Street and Grizzly Road on the southeast side of Madras.
"Roundabouts offer many advantages," according to David Aulwes, landscape architect with Walker Macy of Portland, the design firm hired by the city of Madras to help with urban renewal and related projects.
. "They can significantly reduce the costs associated with a signalized intersection," he said. "Typically, they are cheaper or equal in cost to installing a standard traffic light intersection, with the greatest cost savings in the long-term maintenance of the facility."
. Roundabouts are considerably more efficient than standard intersections, he pointed out. "The average delay at a roundabout is estimated to be less than half of that at a typical signalized intersection. Decreased delay may mean fewer lanes are needed in the overall transportation system."
City Administrator Mike Morgan noted, "It's been in the city's transportation system plan since 1998 as a recommended method to address intersections that qualify based on design issues."
The Grizzly roundabout will be bisected by Grizzly Road to the north and south, J Street from the west to the east, and to the northeast, toward Jefferson County Middle School, City View.
"The J Street/City View/Grizzly intersection would see even greater delays than a typical four-way signalized intersection because it has five roads approaching it," Aulwes said. "The fifth street would greatly complicate the phasing of the signals if it were built as a standard intersection."
. A roundabout is much safer than a standard intersection. Aulwes explained, "They are designed to slow entering traffic and allow all the traffic to flow through the junction freely and safely. The slower speeds mean fewer accidents and a particularly large reduction in serious accidents."
Aulwes anticipates that the roundabout will be able to handle 20,000 vehicles a day. "A standard intersection carrying that many vehicles would likely be two lanes in both directions with a center turn lane and possibly a right hand slip lane," he said.
Two lanes in each direction and a turning lane could require five or six lanes, and a width of up to 60 to 72 feet, compared to a single 14- to 17-foot lane, he said. The narrower roadway allows pedestrians to cross a single lane of traffic and wait on the island in the center of the roundabout before proceeding across the road on the other side.
"The only disappointment I have found, in regard to safety, is that roundabouts have not been found to increase the safety of cyclists," Aulwes said, "although they are no worse than a standard intersection."
. Roundabouts have a smaller area to create runoff from a storm.
. "Roundabouts also have urban design and aesthetic advantages," Aulwes said. "They eliminate the clutter of overhead wires and signal polls and allow signage to be reduced."
The next phase of the J Street project, which is a cooperative effort by the city and the county, will proceed after the new bridge to span Willow Creek is built.
"I think we'll see the bridge constructed before the spring thaw," said Morgan. The county is in charge of that phase of the project.
The second phase of the $2.3 to $2.9 million J Street expansion project will include the connection of McTaggart and Grizzly roads, and the roundabout. The third phase will connect Grizzly to City View and Ashwood Road near the middle school.
"My goal remains to try to have this done by Sept. 30," said Morgan.