Upon crossing the Musconetcong River, I-80 enters Mount Olive Township in Morris County and passes through more woodland with a narrower median. The road comes to a trumpet interchange with US 206 and forms a concurrency with that route as it bypasses Netcong to the south. After turning southeast and passing near suburban business parks, the highway crosses over NJ Transit’s Morristown Line/Montclair-Boonton Line and reaches a partial interchange with US 46. This interchange has only a westbound exit and eastbound entrance. The freeway crosses a small corner of Netcong and Mount Olive Township again before continuing into Roxbury Township, where it comes to a modified cloverleaf interchange. At this interchange, Route 183 heads north into Netcong and US 206 splits from I-80 by heading south. The road continues through wooded areas containing some suburban development as it comes to the CR 631 interchange, which also provides access to eastbound US 46. The road crosses the NJ Transit line again and parallels it a short distance to the north as it comes into Mount Arlington and reaches the Howard Boulevard exit, serving Mount Arlington station. I-80 continues back into Roxbury Township and comes to a westbound truck rest area with the eastbound one being abandoned. After this, the road heads farther north of the railroad tracks and briefly passes through Jefferson Township and Rockaway Township before continuing into Wharton. Here, the freeway has an eastbound exit to CR 634 that provides access to Route 15 before it reaches the interchange with Route 15 proper that lacks an eastbound exit.