Route 347 upgrade in South Setauket aims to boost safety at dangerous intersection

State highway crews have started work on a nearly $45 million project near Lake Grove aimed at improving safety and traffic by adding an extra lane and more traffic signals along Route 347.

The project is the seventh phase of ongoing work over the past 15 years to modernize 12 miles of Route 347 between Routes 25A and 454.

It will add a third lane from Hallock to Nicolls roads on Route 347 to increase the flow of traffic. The speed limit will be reduced to 45 mph and new enhanced traffic signals and crosswalks will be added to one of Long Island’s most dangerous intersections for pedestrians.

From 2014 to 2023, there were 586 crashes at the intersection, including 13 serious-injury crashes and one fatality, according to state transportation data compiled as part of Newsday’s Dangerous Roads project.

"It’s a bit nerve-wracking and challenging," said Elissa Kyle, an architect and placemaking director at the nonprofit Vision Long Island, which advocates for more walkable downtowns.

"I try to stay away from roads like this because they’re stressful to drive on so if I can avoid them," Kyle added, "I generally do."

The latest part of the decadeslong project will also add raised stone medians with Long Island native plants. Construction is expected to create more than 580 jobs and be completed by 2027, state officials said.

State officials said they have invested more than $250 million in Route 347 improvements since 2010.

The project also includes setting back bus stops away from the flow of traffic and extending the parallel biking and pedestrian Parks to Port Greenway path, which is planned to run 15 miles along the road between Hauppauge and Port Jefferson Station.

"We are reimagining the State Route 347 corridor to better accommodate the evolving needs of Long Islanders and make it easier and safer for motorists, pedestrians and mass transit riders to travel along this important roadway," Gov. Kathy Hochul said in a statement announcing the construction project.

Route 347 connects central Long Island to the North Shore and sees about 60,000 vehicles daily. Also known as the Smithtown Bypass, it runs past business offices, restaurants and the Smith Haven Mall.

"This part of Long Island was developed after building for cars was the norm. This place was farms before it was built for cars," Kyle said. "It’s a huge step in the right direction. We need to see more of this on Long Island that offers more alternatives and safer ways to get around that don’t require people using cars."

The state Department of Transportation previously announced plans to begin construction in 2028 on a bridge overpass at Nicolls Road that is expected to be completed in 2031. The bridge is estimated to cost between $110 and $140 million.

Additional phases of the project include continuing construction on Route 347, one mile east of Nicolls Road, from Mark Tree to Old Town roads, and then from Old Town Road to Route 25A, state officials said.

NewsdayTV's Shari Einhorn contributed to this report