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What the new, experimental mini roundabout in Shakopee could look like.

, Federal Highway Administration

To watch a video on it, go to www.startribune.com/a1042.

'Mini-roundabout' could make debut in Shakopee

  • Article by: DAVID PETERSON
  • Star Tribune
  • February 14, 2012 - 2:38 PM

Shakopee could become a guinea pig in a quest for cheaper new ways to keep traffic moving.

The state and federal governments are looking for volunteers willing to test out the next generation in roundabouts: a so-called "mini" version, much cheaper than the standard ones and with both benefits and potential drawbacks.

"We're pushing for new techniques to save money," said Scott County's public works chief, Lezlie Vermillion, "and our success or failure would be right out there in public. In fact, public acceptance would be one thing we'd be testing."

The mini-roundabout doesn't expand an intersection at all. It merely plants a circle in the middle and sends folks around it.

That means there isn't enough room for trucks or buses to wriggle their way around. So the circles are configured in such a way as to allow those big vehicles to just slam right across them, almost as if they weren't there.

One big question for Minnesota: How does that work in snowy weather? If you're going to raise the circle enough to keep cars but not trucks or buses off of it, can you also plow it?

"One thing we need to look at," Vermillion said, "is that maybe it works great in Phoenix, but with our snow is it more of a struggle here."

Still, the potential cost savings is huge -- enough to make some puzzled elected officials at both the county and city levels willing to at least push for a piece of the money that's out there to lure volunteers to step forward.

"We've discussed it very briefly," said Shakopee Mayor Brad Tabke. "It's a possibility if the grant comes through, but it has not been discussed in depth or approved."

Consider the facts:

At County Road 79 and Vierling Drive, a fairly busy intersection with a four-way stop, traffic at peak times can back up for three blocks.

To put in signals, and accelerate traffic that way, would easily cost $500,000 -- about half for the signals themselves, and more to widen the roads and create turn lanes.

The cost to convert to a mini-roundabout: less than $100,000.

The state has $200,000 and will choose two volunteers.

"We asked a lot of questions," said County Commissioner Jon Ulrich, "but the fact is roundabouts have been working really well up to now, despite the skepticism at first."

Ulrich's own city of Savage, said Vermillion, was "not totally keen on the idea when we first proposed them, but now they want us to evaluate roundabouts at every signalized intersection."

Along with cost, safety is a big lure. At the Vierling intersection, between 2008 and 2010, officials documented 12 crashes -- a rate of 0.9 per million vehicles entering. That's nearly twice the metro and statewide average for all-way stops.

Meanwhile, because it's mainly residential, there are relatively few large trucks. There are schools nearby, but someone went out and counted, and found only 11 buses in the morning and eight in the afternoon.

Ironically, one thing that could prevent Scott County from getting the grant, which is being given in a partnership between the state and federal governments, is that traffic volume at the Vierling intersection is approaching the upper limit that's part of the criteria.

An intersection needs to have fewer than 1,400 vehicles per hour to qualify, and this one is creeping toward that point, Vermillion said.

But in an era when saving $400,000 is nothing to sniff at, the new format may begin to spread, grant or no grant.

David Peterson • 952-746-3285

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