Milltown road is a road that connects 22 (and even 28) to 202, and goes all the way into Raritan.
If you drive down 22, going West to East, these are the roads:
Rt 28/Easton Tpke
Country Club Rd
Rt 22 overpass
If you're going West from the East, it's the other way around. Just take Milltown road between 202 and 22 and you'll find it. There's a parking lot and very high lights that stay on until about 10:45pm.