- Southern Terminus:
- US 9 in Beachwood
- Northern Terminus:
- US 9 and Garden State Parkway (NJ 444) in Toms River
- 3.73 miles
NJ 166 is a short north/south route in Beachwood and Toms River through the area where US 9 is routed along the Garden State Parkway (NJ 444). It has both of its termini at US 9 and serves as the functional equivalent of a business route despite having its own route number. The entire length is a two-lane undivided road with traffic lights.