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Driving in circles

''So, who invented the rotary?'' I asked E. Pagitsas, manager of traffic analysis and design for the Boston Metropolitan Planning Organization. ''And exactly how was he put to death?''

Pagitsas chuckled at the question, but she knew what I was talking about. We all know what I'm talking about: Choose your rotary -- the Arborway in Jamaica Plain, Route 16 in Somerville, Kosciuszko Circle in Dorchester -- and you'll find endless horror stories. Nobody slows down; nobody yields; nobody lets you exit; nobody cares.

``Very few people seem to adhere to the `drivers in the rotary have right of way' rule," writes reader Jocelyn Hutt of Roslindale, ``which makes being in the rotary almost as dangerous as trying to get in or out of the rotary."

``It's a free-for-all," gripes reader Michael Gavin of West Roxbury , ``with the victor usually being the most intimidating driver."

So, how does one survive a rotary? And can you do so while still obeying the law?The law says

Most drivers know the general rules from driver education class. When entering a rotary, you're supposed to yield to cars already in the rotary. Once in the rotary, you're supposed to drive in the inside lane until approaching your exit. You then return to the outside lane and exit.

But if the rules are so simple, then why are rotaries so dangerous?

Mark Raisman, the owner of Jamaica Plain's Colonial Driving School, says drivers know the law, but just aren't courteous toward fellow motorists.

Somerville Police Chief Robert Bradley says that when a rotary is badly congested, drivers often have no choice but to butt their way into it. ``You don't yield; you try to merge," he says.

Others point out that while rotaries are fairly indigenous to New England -- we adopted them from mother England -- out-of-state drivers often have no idea how to react when they encounter them, making more problems for all.

Pagitsas says the reason we have so much difficulty navigating rotaries is largely because of their poor engineering design, or, more accurately, their badly out-of-date design.

That's right, fellow Boston drivers: It might not be all our fault.

``Large rotaries allow for high-speed merges and diverges, like the circle around the Arc de Triomphe in Paris," she says. ``Also something like the Concord Rotary is a pretty big rotary -- or the Sagamore Rotary. When they first designed rotaries, people were not driving at these high speeds. Or maybe they couldn't drive fast. But they do now."

Thankfully, nobody builds rotaries, also called traffic circles, anymore, Pagitsas says. Engineers instead design ``roundabouts," which are essentially miniature rotaries with specific features that force drivers to behave properly.

While rotaries have multiple lanes, roundabouts are usually one lane wide, so drivers can't weave between inside and outside lanes or get outmaneuvered by more aggressive drivers.

Old rotaries have uneven traffic flows. The feeder road you're traveling on may account for 10 percent of the cars entering the rotary, but if the feeder road to your left accounts for 50 percent of the cars entering the rotary, you're going to have to muddle through a logjam.

As their modern replacements, roundabouts have more evenly distributed traffic flows, and because they're smaller -- about 60 feet across, compared with 200 feet across for a rotary -- they don't allow drivers to build up a lot of speed. Roundabouts also incorporate a concept known as deflection, which basically means that you can't make a speedy, straight line to your exit.

It all sounds so nice.

Our big, old rotaries will probably gradually disappear as road improvements are made over time, Pagitsas says. Until then, about all you can do to stay safe is keep on yielding.

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