West Tisbury and Edgartown this week took the Martha’s Vineyard Commission to court seeking to block the roundabout project that has become a lightning rod over periodic traffic congestion at the center of the Island.

In their lawsuit filed in Dukes County superior court on Wednesday, the two towns seek to invalidate the commission’s Oct. 6 decision – which was affirmed on Nov. 3 — and force a more thorough review of the proposed project planned for the blinker intersection of Edgartown-Vineyard Haven and Barnes Roads.

The complaint claims the commission “failed to adhere to several of its own procedures and regulations regarding the consideration” as a development of regional impact (DRI).

Among other things, the lawsuit said, the commission voted approval before its own land use planning committee had an opportunity to make a recommendation to the full commission and instead relied on preliminary design plans that were 25 per cent complete.

The complaint also said the commission did not comply with a requirement that a traffic impact analysis be reviewed by independent engineers, and failed to make required findings about the project’s impact on other towns.

“The single most common thing you hear is the [project] was rushed through,” said attorney Richard W. Renehan, who is representing the two towns, in an interview yesterday. “I think if they had taken more time . . . who knows how it would have come out?” added Mr. Renehan, who is a partner with the Boston firm Goulston & Storrs.

The MVC will be represented by Brian Hurley, of Rackemann Sawyer & Brewster, but Mr. Hurley declined comment until he had a chance to review the lawsuit.

The commission issued a statement this week saying it intends to “vigorously defend” its decisions to fulfill its mandate to “protect the character and environment of Martha’s Vineyard.”

“The commission believes that it thoroughly and properly reviewed this proposal, that its review benefitted from the perspectives offered by the public and the commissioners, and that thecourt will give deference to the commission’s expertise and efforts, and uphold the decision,” said chairman Chris Murphy in the statement.

The next step in the litigation is for the MVC to submit a formal legal response in the coming weeks.