The route runs through Ocean Township, Marlboro, East Brunswick, and is the main thoroughfare for Rutgers University.

Much of the route is a freeway (including the entire portion in Monmouth County and much of the northern end through New Brunswick and Piscataway).

The freeway continues to the northwest through wooded land for several miles, crossing over Normandy Road and to the south of the Pebble Creek Golf Club.

After interchanging with US 9 (exit 30), the freeway ends, and the route becomes a four-lane expressway, and then an arterial road through a mostly wooded commercial stretch of Old Bridge.

Following an intersection with Eggers Street, Route 18 becomes a six-lane expressway and crosses over the New Jersey Turnpike (I-95) at exit 9.

[3] The interchange with US 1 is followed by an intersection at Paulus Boulevard before becoming a six-lane freeway and separating into a local–express configuration and paralleling the Raritan River, passing the former New Brunswick city docks.

As Hoes Lane, Route 18 becomes a four-lane arterial road and passes Resurrection Cemetery of the Diocese of Metuchen, as well as the post office and township hall of Piscataway, before reaching an intersection with Centennial Avenue.

Route 18 turns on Centennial Avenue and continues for about 0.3 miles (0.48 km) to a traffic signal for Possumtown Road.

From this intersection, Route 18 is considered to exist both on Centennial Avenue and Possumtown Road, and ends in each case at the respective entrance ramps for Interstate 287.

Both plans were endorsed by the Tri-State Transportation Committee in 1962, and the acquisition for the right-of-ways began almost immediately.

Outside of the bridge, there was significant controversy over the abandoned Delaware and Raritan Canal heading through New Brunswick.

[15] In 1977, the newly formed New Jersey Department of Transportation received a federal grant to construct the Route 18 from New Street in New Brunswick, across the Raritan and terminating at CR 514 Spur in Piscataway.

Conti Enterprises was hired for the project, which was announced complete in August 2009 at a ceremony by governor Jon Corzine and Stephen Dilts, the commissioner of the New Jersey Department of Transportation.

The area of the Paulus Boulevard intersection was upgraded for accessibility, and a bus stop was installed, but the roadway southbound is still three lanes at the traffic light.

The state acquired 12 homes along the existing Metlars Lane and 30 acres (120,000 m2) of land from Rutgers to build the extension.

Some of the right-of-way that was acquired in the 1960s for the Route 35 freeway were transformed into a multi-use trail for bicycles and other vehicles to link the Wall Township Municipal Complex to the existing Edgar Felix Bikeway that runs from Manasquan to Allaire State Park.

[23] NJDOT is in planning to create a Park & Ride at the southern terminus of the Route 18 freeway.

Residents are in opposition to this proposal for fear of loitering and vandalism that may accompany the parking lot.

The Old Bridge improvements include adding inside shoulders and widening County Routes 516 and 527.

As of the end of 2009 the large project was put on hold because of the lack of funds and the economic situation.