From here, US 1 continues northeast as a surface divided highway through suburban areas, heading into Middlesex County and passing through New Brunswick and Edison.

US 1 merges with US 9 in Woodbridge, and the two routes continue through northern New Jersey as US 1/9 to the George Washington Bridge over the Hudson River in Fort Lee.

[1][2] As the road heads through the downtown area with Amtrak's Northeast Corridor railroad line running next to the route on the east side, it has a southbound exit and entrance with Warren Street that provides access to the New Jersey State House.

[1][2] At this point, the Trenton Freeway turns onto a depressed alignment, with Conrail Shared Assets Operations (CSAO)'s Enterprise Industrial Track railroad line closely parallel to the east, and comes to an interchange with Perry Street.

[1] Past this interchange, US 1 continues into Lawrence Township, where the surroundings become more wooded as the freeway has an exit for Whitehead Road.

[1] Here, US 1 becomes a four-lane divided surface road with jughandles called the Herbert Highway that is lined with suburban businesses.

Past this point, US 1 widens to six lanes as it has an interchange providing access to Quaker Bridge Mall to the southeast of the route.

[2] Studies are being conducted to implement the Central New Jersey Route 1 BRT, a bus rapid transit system utilizing the highway that would radiate from Princeton Junction station.

[3][4] Upon crossing the Millstone River, US 1 enters Plainsboro Township, where it passes more business parks and comes to an interchange with Scudders Mill Road.

The route continues into South Brunswick, where it narrows to four lanes and runs through a mix of rural areas and development.

[1] The road passes by Rutgers University college farm before turning northeast and coming to a cloverleaf interchange with Ryders Lane.

[1][2] Upon crossing the Raritan River on the Donald and Morris Goodkind Bridges, US 1 enters Edison and continues north into developed suburban areas before turning northeast and meeting CR 514 (Woodbridge Avenue) at an interchange.

[1][2] The route continues northeast into Woodbridge Township, where it comes to a partial interchange with the Garden State Parkway.

[2] US 1 passes over CSAO's Port Reading Secondary railroad line and crosses Green Street (CR 604) prior to merging with US 9 at a southbound exit and northbound entrance.

US 1/9/US 46 come to an interchange with I-95, US 9W, and Route 4, where it joins I-95 to head east to the George Washington Bridge over the Hudson River.

[24] During the development of the Interstate Highway System, New Jersey and Pennsylvania considered having I-95 cross over the Trenton–Morrisville Toll Bridge and continue north on the existing US 1.

The project was opposed due to inadequate highway standards (lack of shoulder ramps, and only two lanes in each direction).

[25] By 1969, an extension of the Trenton Freeway from the current left-hand exit to US 1 Bus./US 206 to Whitehead Road was completed and received the Route 174 designation.

It was to begin just north of the intersection of Ridge Road and US 1 in South Brunswick and terminate at the mainline of the New Jersey Turnpike (I-95) at exit 8A in Monroe Township.

[30] By the 1990s, many traffic lights along the segment of US 1 in West Windsor and Plainsboro were removed and replaced with exit ramps and overpasses.

[32] An environmental impact study has been conducted by Rutgers University’s Transportation Policy Institute and Center for Negotiation and Conflict Resolution to improve US 1 through the Penns Neck area.

[33] This project would eliminate the Penns Neck Circle where US 1 meets Washington Road (CR 571) and move US 1 onto a new freeway alignment in the area.

[34] In 2009, the segment of US 1 between I-287 in Edison and the Garden State Parkway in Woodbridge was rebuilt to include new ramps at several intersections and removed access to a couple of roads in a $53.9-million (equivalent to $74.4 million in 2023[35]) project that was intended to alleviate traffic and make this section safer.