The Five Corners intersection took center stage at the Martha’s Vineyard Commission this week as public discussion began about potential traffic impacts from the planned Stop & Shop expansion in Vineyard Haven.

Traffic planners for both the commission and Stop & Shop said the notorious intersection, where five roads converge and few traffic controls are in place beyond driver courtesy, confounds traditional methods for analysis.

The 30,500 square-foot supermarket expansion plan is under review by the MVC as a development of regional impact. A public hearing on the plan continued Thursday night.

Located half a block from the planned grocery expansion site and also the main Steamship Authority terminal in Vineyard Haven, Five Corners sees an influx of traffic when ferries arrive and depart. There is police control at the intersection only when ferries arrive and at times when the Lagoon Pond drawbridge goes up.

Keri Pyke, a traffic engineer who peer reviewed the grocery chain’s traffic studies for the MVC, said another complicating factor is “the unusual courtesy of Island drivers,” as people who do not have stop signs sometimes stop to let others turn. She called this phenomenon “virtually impossible to model.”

The traffic analysis uses data collected during mid-July from morning to late afternoon.

Stop & Shop traffic engineer Randall Hart said the project is expected to generate 144 trips on weekdays during evening peak hours, and 147 trips during the Saturday midday peak hours from 11 a.m. to 2 p.m. The proposed project would generate 108 new car trips (49 entering and 59 exiting) on weekdays during evening peak hours, and 110 new vehicle trips (54 entering and 56 exiting) during the Saturday midday peak hours.

Mr. Hart said the project is expected to cause a five per cent increase in traffic volume at Five Corners. Even if the majority of the trips go through Five Corners, he said, the intersection will see less than a seven per cent increase. He described the numbers as very conservative.

Mr. Hart said there would be an impact on traffic from the new store, and it would be minor.

Ms. Pyke expressed concern about the ability of the modeling to predict real-world conditions. “We are still left wondering how we can compare the future conditions and assess the impact of the expanded store on traffic in Five Corners,” she wrote in a Nov. 20 memorandum to the MVC.

Ms. Pyke disagreed with the prediction that 80 per cent of traffic coming from up-Island via State Road will use Main street and Norton Lane to access the store. She said it was more likely that 80 per cent of the traffic would go through Five Corners.

Stop & Shop has proposed mitigation measures, including updating signage and updating and restriping the road on Water street. Other measures include adding a police officer to control traffic at Five Corners and Water street during peak summer hours, encouraging and adding incentives for employees to park off-site, and making pedestrian and landscaping enhancements.

They are also offering to give the town of Tisbury $20,000 for transportation improvements and have offered to work with the town on other transportation issues, including talking with the Vineyard Transportation Authority.

Mr. Hart said truck deliveries to the new store will be similar to the existing delivery schedule, with one tractor trailer arriving at the store each day and 10 to 15 vendor trucks.

Issues around delivery trucks and staging and construction will be addressed at the next public hearing, which is scheduled for Jan. 9.

Commissioners expressed interest in having a police presence for more than one hour during peak traffic periods. Some pointed out that backups often extend to Main street and up to the Edgartown-Vineyard Haven Road intersection.

“Does anyone have a suggestion that would be a quick fix on this traffic situation?” commissioner Clarence A. (Trip) Barnes 3rd asked. “It’s a mess and it’s going to continue to be a mess but we’ve got to have the grocery store straightened out.”

VTA administrator Angela Grant registered concerns about impacts on the regional Islandwide bus system, whose frequent trips in and out of the area operate on a tight schedule. “While there are differing options as to degree of impact, the reality is they are noteworthy,” Mrs. Grant said. She suggested that Stop & Shop purchase annual bus passes for employees, provide financial incentives to take public transportation, and should not allow employees to park on-site. She further suggested that Stop & Shop should begin a home delivery program.

“The detriment is going to be longer trip times, which will mean fewer trips and diminished capacity,” Mrs. Grant said. She said Stop & Shop “should be required to pay for this impact on the Island. They should be required to contribute to the cause.”

Tisbury planning board member Dan Seidman questioned the impact of going from a seven minute queue to a nine minute queue. “Are we all in that much of a hurry that two minutes is life or death?” he asked.