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Roundabout

Circular intersections may help traffic woes

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A booming population, exponential growth and development--great for the economy, not so much for a road system already struggling to keep up with the existing population.

Ada County's traffic woes are plights familiar to anyone who lives in, or even visits, the valley. Now, traffic engineers are preparing to bring an alternative to Boise as plans move forward to build two roundabout intersections.

Both projects--one slated for the intersection of Warm Springs Avenue, Granite Way and Old Penitentiary Road, and the other at Hill Road, 36th Street and Catalpa Road--are scheduled for construction in 2009. They'll be the first roundabouts in the city to carry heavy traffic.

The circular intersections, used widely across Great Britain and Australia, are a takeoff on the old-style traffic circles. They turn a four-way intersection into a circular drive with cars entering and exiting when needed. There are no traffic lights.

Even though vehicles move at a slower speed, research done by the Insurance Institute for Highway Safety shows that roundabouts allow more cars to pass through these intersections faster.

Until this point, roundabouts have only been found in subdivisions in Boise. They were considered for past projects, but the public reaction to them was so poor, they were quickly pulled off the table, according to Ross Oyen, traffic engineering supervisor for the Ada County Highway District. But after watching other communities successfully use roundabouts, the idea has returned.

"They're going in around the country," Oyen said. "A lot of states are ahead of us, but that's fine. We can look at other people's lessons, good and bad."

Already, the tri-city area around Seattle boasts more than 100 roundabouts, and Bend, Ore., is studded with the circular intersections. Nampa installed its first one at the corner of Happy Valley and Amity roads.

Now, ACHD is preparing for the future of roundabouts in the valley. ACHD is also studying Amity Road between Eagle Road and the Ada County line as a possible roundabout corridor, with roundabouts placed approximately every mile.

One person who already has a good idea of what to expect when it comes to roundabouts is Mark Lenters, president of Ourston Roundabout Engineering, the only traffic engineering company in the country focusing only on roundabouts.

Lenters is working to help design roundabouts throughout the Harris Ranch project off Warm Springs Avenue and said the use of the traffic devices in that development shows advanced thinking. "It's rare that you see that much population and not have a traffic signal somewhere in the development," he said.

Lenters has focused solely on roundabouts since 1999 and has seen them solve some big problems when it comes to both congestion and safety.

"You don't have high-speed turning movements," he said, listing the benefits of roundabouts. "It's also a very passive form of speed control--geometry dictates the speed."

Insurance Institute studies tout the improved safety at roundabouts compared to traffic signals. Lenters cited one in particular, which showed a 76 percent reduction in injury crashes at 55 intersections where roundabouts were installed.

"Traffic engineers are obliged to consider a device with that much potential," Lenters said.

The biggest drawback to roundabouts is they are still relatively unfamiliar to most people in the United States.

"You have to be on the ball to get into the circle," Lenters said. "You can't have the coffee in one hand and the cell [phone] in the other."

They are also a concern emergency-response crews. In August 2005, the Bend Bulletin reported that emergency and law-enforcement crews found that, on average, having to move emergency vehicles through roundabouts instead of traditional intersections slowed down their response time.

While cities may be slow to embrace roundabouts, the residents of the East End Neighborhood Association aren't.

"We picked up the idea and ran with it," said Rocky Bogert, vice president of the association.

"The primary [reason] is the fact that it's also a major north-south link in the Ridge to Rivers pathway system, there's also a city park and the botanical gardens--there's a lot of traffic there," he said.

In addition to easing access to the Old Idaho Penitentiary, the Idaho State Botanical Gardens and Warm Springs Estates, Bogert said residents embraced the idea as a way to get traffic to slow down when heading back into the city from the east.

"The posted speed is 30 mph; the average speed is 39 mph," Bogert said.

The association even helped secure $300,000 in federal grant funding for the roundabout landscaping and a set of arches flanking either end of what will be called the Historic Warm Springs Neighborhood. The two sandstone arches with metal-framed archways will stand at Avenue C, near East Junior High School, and the planned roundabout.

Federal funds can only be used for the arches and landscaping, but ACHD must pick up that cost of the roundabout--an as-yet-unknown figure awaiting final design changes. As currently planned, the roundabout would be 110 feet in diameter, with islands in between lanes for pedestrians.

Of course, adding a roundabout to an existing neighborhood is never a clear-cut process.

Warm Springs homeowner Charles Gill likes the concept of a roundabout, but not the reality of the limited access it poses to his property, should the project go forward as planned.

"The first draft of the roundabout plan really trashed our property," he said. "We took immediate steps to try and repair that, which resulted in modifications of the plans. It's somewhat better, but we're not out of the woods yet."

Gill said he and his wife have been trying to work with the neighborhood association to make the necessary changes, but many issues still remain.

Neighbors near the Hill Road/36th Street/Catalpa Street site have also had concerns over the years. The idea for the roundabout was first examined several years ago, but was rejected because of its proximity to Hillside Junior High School. ACHD's solution was to realign the roads to create two T-intersections a short distance apart. The idea didn't go over well with area residents.

After looking at the roundabout option again, ACHD discovered that other cities had successfully used roundabouts in similar situations. Now, the plan calls for a roundabout 250 feet across, with enough center-island room to allow for future expansion. Estimated price: $1.5 million.

While the future of roundabouts in Boise will likely be measured against the success of pending projects, Lenters sees them as a viable option for the city's congestion woes.

"Anywhere there is a potential that you might need a traffic light, it's a suitable location," he said.

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