After 10 years of planning and debate this week the public will have what may be their final say on the proposed roundabout in Oak Bluffs. On Thursday the Martha’s Vineyard Commission will hold a hearing at 7:15 p.m. at the high school cafeteria, not far from the controversial intersection where the Edgartown-Vineyard Haven Road meets Barnes Road.

The commission has received a blizzard of letters over the past few weeks, some praising it as “intersection improvement,” and others deriding the proposed traffic solution. All of Oak Bluffs’s public safety officials support the roundabout. Islanders are not uniformly sold on the idea, however; new “Stop the Roundabout” bumper stickers have begun appearing around the Island.

“This ‘big city idea’ will help ruin the charm and sensible driving habits on the Island and doesn’t do anything to promote safety,” John Alley of West Tisbury wrote to the commission.

“I think this is one bit of MV ambience that needs to change,” wrote Sharry Grunden. “This used to be a major accident intersection. The four-way stops have helped a great deal and the roundabout will improve it some more.”

The roundabout, the subject of a decade of planning, is set to go out to bid this fall. Oak Bluffs selectmen began studying the blinker intersection in 2001 by hiring an independent firm which recommended a roundabout. After a number of accidents, town selectmen made the intersection a four-way stop in 2003 and approved in principle the construction of a roundabout. In 2004 the selectmen asked the MVC to study the intersection and in 2006 the commission released a report also recommending a roundabout. In the same year the town held three public hearings about the proposal; the state Department of Transportation held another public hearing this spring.

In June this year Oak Bluffs voters approved $3,000 to purchase easements in what many thought was the final obstacle to the project’s construction. But later that month the roundabout was referred to the MVC for review by the West Tisbury selectmen, who felt that more public discussion was in order. And at a public hearing at the commission earlier this month, commissioners agreed that the proposed traffic intersection was plainly of regional impact, citing potential impacts on the intersections at either end of the Edgartown-Vineyard Haven Road.

On August 26, the engineering firm Greenman-Pedersen Inc. provided a response to a number of questions posed by the Martha’s Vineyard Commission, including those about the relative safety of roundabouts compared to other traffic intersections, the roundabout’s potential impact on congestion at the Barnes Road intersection as well as its potential impact on intersections at either end of Edgartown-Vineyard Haven Road.

In that response Greenman-Pedersen director of traffic engineering John Diaz cited information from the Insurance Institute for Highway Safety, claiming that roundabouts — not to be confused with larger and faster rotaries — reduce injury accidents by 75 per cent and fatal accidents by 90 per cent, increase traffic flow up to 50 per cent, decrease fuel consumption by as much as 30 per cent and cost less than traffic signals as they do not require expensive equipment or maintenance. One of the main contributors to the relative safety of roundabouts is the fact that there are 32 collision points possible at a four way stop and only eight at a roundabout, Mr. Diaz said.

Regarding congestion Mr. Diaz writes that in the summer months, delays, especially eastbound on Edgartown-Vineyard Haven Road, can top three minutes at the current four-way stop. By 2030 Greenman-Pedersen Inc. estimates that number could jump to nearly seven minutes — compared to a mere 13 seconds with a roundabout. Such dramatically improved efficiency in the heart of the Island poses the obvious question, what will that do to the already congested intersections in Edgartown and Vineyard Haven?

Some Vineyard residents, including architect Craig Whitaker, think the answer is obvious.

“The inexorable facts are that the faster you get to the Triangle the longer you must wait there,” he wrote in the Gazette commentary pages this month.

But Mr. Diaz says that isn’t so.

“Simply converting from the four-way stop control to a roundabout results in an increase of only 14 vehicles per hour eastbound and approximately five vehicles per hour westbound,” he writes. “This translates to one additional vehicle approximately every four to five minutes eastbound, which given that the intersection of Beach Road is more than four miles away is insignificant.”

Mr. Diaz says that locations between Vineyard Haven and Edgartown, such as the high school, the YMCA and County Road would also siphon traffic away from those intersections.

At a public hearing at the commission in August Mr. Diaz said that by comparison a traffic signal, favored by some Islanders, by releasing a long line of traffic all at once, would have a more substantial negative effect on congestion at either end of the highway.

The state average for accidents per million vehicles entering intersections similar to that at the four-way stop is .55. From 2006 to 2008 the state recorded a rate of .83 at the four-way stop, a number that reflects 12 accidents.

If approved, the roundabout project would be paid for with $1.2 million in state and federal Transportation Improvement Project money, which is funded in part by a surtax on gasoline.