SEEKONK — Traffic engineers Weston & Sampson have determined that installing a roundabout at Fall River and Arcade avenues would be the best way to improve safety at the busy intersection. A roundabout, officials told the Board of Selectmen last night, would also require fewer potential property seizures and would have less impact on nearby wetlands than other options for that junction.

The engineers last night presented preliminary concepts for three options to upgrade the sometimes-dangerous intersection: a T-shaped intersection with two lanes each way on Fall River Avenue; a four-way intersection, again with an extra travel lane on Fall River Avenue, that would require moving Mill Lane to align with Fall River Avenue south; and a roundabout, which wouldn’t require additional travel lanes or use designated turning lanes like the other options.

All three options would work, the engineers said, but the roundabout would mean less intrusion on town-owned conservation land bordering the roadways and less impact on abutting properties that might need to be seized to widen the road for the two signalized options.

A roundabout would also be safer, because drivers would be forced to slow down as they approach the roundabout, probably to speeds of 15 mph. Traffic would continuously flow as opposed to halting for a traffic signal.

The cost estimate ranges from $1.5 million for a roundabout to $2 million or $2.5 million for a stop-light intersection. MassHighway would finance the project, which likely wouldn’t be tackled until 2010 at the earliest.

The intersection is rated one of the worst in Bristol County.

Traffic counts taken in 2006 showed 1,000 cars travel north through the intersection on Fall River Avenue, also known as Route 114A, during the evening commuting hours. About 930 vehicles pass through in the busy morning hours. The resulting backup for those traveling south on Arcade Avenue is the reason that road is rated “F,” the state’s worst designation.

The selectmen last year had voted against the roundabout idea. Their wariness was tempered last night.

Selectman John Whelan said he worried that all of the options would still result in peak-hour traffic backups at Luthers Corner, at County Street and Fall River Avenue.

“How do they know to blend” into the roundabout? Michael H. Brady asked. “I’ve just seen people drive for 23 years [as a Rehoboth policeman] and everyone is in a rush. No one wants to be courteous.”

Brady said he’s also concerned about how a roundabout might affect the travel of fire apparatus through that intersection. The engineers said there would be room for vehicles to pull aside to let fire trucks and rescue wagons pass without delay.

Carol M. Bragg suggested the engineers might want to consider making Arcade Avenue a one-way stretch northbound to the Taunton Avenue stoplight, an option Weston & Sampson had not examined.

“Roundabouts are new,” said David Cabral, the town’s assistant public works superintendent. “The studies have been done that show there’s a negative attitude prior to them being constructed, but there tends to be a positive attitude once they’re built.”

A public hearing will be held once the engineers are further along in the design phase of the roadway improvements.

In other action last night, the selectmen formalized its decision to reject the town’s reserve capacity at the Attleboro wastewater treatment plant, citing hefty costs the town would face for an environmental upgrade at the plant.

mwims@projo.com