Mercer County opens new bi-county bridge over Millstone River
Mercer County officials on Monday opened a newly constructed bridge over the Millstone River, restoring a key connection between Millstone Road in West Windsor Township and Grover’s Mill Road in Plainsboro Township, Middlesex County.
The bridge, known in Mercer County as Bridge #760.4 and in Middlesex County as Bridge #4-B-92, replaces a steel multi-beam structure built in 1967 that had been deemed structurally deficient and functionally obsolete.
The new bridge is a single-span, multi-beam structure supported by a precast reinforced concrete pile cap founded on steel piles. Its superstructure consists of a prefabricated composite concrete deck on steel girders, a design intended to improve durability and extend the lifespan of the crossing.
The bridge reopening restores a direct route for residents and travelers moving between Mercer and Middlesex counties and should alleviate traffic backups in the area.
The former bridge was closed to traffic in July 2025 to allow construction to begin. Midatlantic Construction LLC of Barnegat Township was awarded the project through a competitive bidding process.
County officials said construction was substantially completed in 154 calendar days, aided by advanced building methods that included the use of precast segments and ultra-high-strength concrete closure pours.
The project also included roadway improvements on both sides of the river. Officials said the bridge now meets all New Jersey Department of Transportation standards and features new sidewalks, open bridge railings, and guide rail at the leading corners. The connecting roadways were repaved, restriped, and upgraded with new sidewalks.
“I’m proud that we were able to complete this work quickly, replacing an outdated structure with a safe bridge that will stand for many decades to come,” Mercer County Executive Dan Benson said in a statement.
