- Southern Terminus:
- Lamberton Road in Trenton
- Northern Terminus:
- Trenton Freeway (US 1) in Trenton
- 2.41 miles
NJ 129 is a short north/south route in Trenton that connects the NJ 29 expressway to the Trenton Freeway (US 1). It begins at Lamberton Road as what is effectively a long ramp that merges with the ramps from NJ 29 to form a four-lane divided highway. There are traffic lights at all intersections, but there are also overhead green signs as if it was an expressway. After a couple of miles, it merges into the Trenton Freeway (US 1) and ends.