Look left, and yield


Once upon a time, the traffic planner’s toolbox for designing an intersection was simple. At the quietest corners, you planted a couple of stop signs, and at busier ones, four. If traffic was too heavy for stop signs, you escalated to traffic lights, and if it was too busy for lights, you ordered an overpass.

Back in a corner of that toolbox, for more than a century, has been the alternative of the circular intersection. Some historians date the roundabout to 1903, when a “gyratory” system was created at what is now the Place Charles de Gaulle in Paris. The modern roundabout — the one-way circular intersection designed to increase safety, ease congestion, and reduce air pollution and fuel consumption — dates to the past half-century, during which it has become the traffic planner’s solution of choice across Europe, and more recently also in the United States.

Roundabouts like the one that’s being proposed for construction at the “blinker” intersection in Oak Bluffs are a mature technology, supported by a body of research that could fill a small reference library. This literature, if you take the time to study it, is tremendously reassuring.

Safety is the roundabout’s strongest suit. A 2001 study by the Insurance Institute for Highway Safety looked at 23 intersections that were converted from stop signs or traffic signals to roundabouts, and found that crashes were reduced by 40 percent overall. Better still, crashes involving injury fell by 80 percent.

This huge gain in safety is attributable mainly to two factors: Unlike intersections controlled by traffic signals, roundabouts create no incentive to either hit the gas when a light turns yellow or to stand on the brake when it turns red. And unlike four-way stops, with their unending negotiations over who-goes-first, roundabout intersections ask drivers to follow only two simple rules: look left and yield.

That’s right, folks: If you can remember to look left and yield to traffic in the circle, you’ve mastered the modern roundabout. Forget everything you’ve experienced in multi-lane, high-speed rotaries like the one at the Bourne Bridge, because none of that applies.

Reading the concerns expressed at the prospect of an Island roundabout over the past few weeks, I’ve seen the issue of bicycle safety raised several times. Speaking as a cyclist who commutes to work most of the year, I only wish my Island neighbors might show as much concern for my biking safety when they get behind the wheel as they profess when they sit down at their computer keyboards.

Bicycle safety in roundabouts is well covered in the literature – and I’ve also been reassured by watching roundabouts in action on webcams online. Consider that at the blinker today, a cyclist must watch for traffic coming from four directions when trying to cross. A roundabout breaks the same transition into two simpler, single-lane crossings — if you’re willing to take a moment to hop off the bike and use the pedestrian lanes. The good news is that on their trip through the intersection, cyclists or pedestrians need worry only about traffic coming from one direction at a time.

Because motorists aren’t idling, stopping and starting as they do at the blinker now, well-designed roundabouts save America a lot of gasoline. One recent study in Virginia estimated that after the conversion to roundabouts, the savings at just 10 intersections totaled 200,000 gallons per year.

But the most striking statistics I found regarding roundabouts have to do with public opinion before and after they’re built. In community after community, studies have shown how negative attitudes toward roundabouts turn to positive once they’re installed.

Josh Balling, assistant editor at the Nantucket Inquirer & Mirror, reports that this very pattern recently played out on our neighbor island. A roundabout was built there a few years ago, on Sparks Avenue at Hooper Farm Road, and as it happens Mr. Balling navigates it three or four times every day by bicycle or car.

The Nantucket roundabout, Mr. Balling told me this week, “was roundly — no pun intended — criticized at the beginning. People said it seemed like a dumb idea. . . . But there’s certainly no controversy about it anymore. It just sort of fit into the traffic landscape, and nobody complains about it. It has eased traffic at a busy intersection, and I feel just as comfortable going through it on my bicycle as when I’m driving.”

According to Mr. Balling, Nantucket’s roundabout occupies a spot where traffic used to back up for a quarter of a mile during the morning and evening commutes. “That backup really doesn’t seem to exist anymore,” he said. “And I can’t recall any serious accidents there.”

In communities across America, roundabouts have prompted that rarest of journalistic creatures, the apology for an editorial opinion. In Vail, Colorado, a local paper pleaded guilty to “taking stabs” at two roundabout projects and “projecting all manner of doomsday scenarios for the project.” After the roundabouts were voted the most popular public works projects in town, the newspaper had to admit that in fact, folks were navigating them just fine. “What’s more,” the editors added, “the gridlock appears to be gone.”

Yes, I do appreciate that Martha’s Vineyard is a place unique in myriad ways. But we’re not exempt from the laws of physics or traffic flow. The guess here is that within a year of the roundabout’s construction at the blinker, we’ll all be safer and happier traversing what was once one of the Island’s most irksome traffic spots.