I approached the summit from the west side. Howard Boulevard, north of I-80, passes through a commercial area, then climbs steeply up the hill of Mount Arlington.
The road shown on the topo that heads east from Howard Boulevard to within a quarter mile of the summit is Larson Lane. Unfortunately, access to the woods at road's end is blocked by private property. The key is to enter the unnamed road lower down the hill signed for the Berkshire Valley Wildlife Management Area (WMA). It ends at a large parking area that gives access to a network of old woods roads and trail. The parking lot is visible on aerial photos and is located just below the letter "d" in the "Pond" of Dunlap Pond on the topo.
From the parking lot, take the trail uphill toward the NE. It soon joins a woods road, and shortly thereafter reaches a four-way junction. Continue straight ahead at that junction and follow the woods road for about a half-mile, all the way to summit, gaining about 250 feet. The summit is marked by a three-foot high boulder and contains the four concrete footings of a long-gone tower. I surmise the woods road was the old access road for the tower. The route passes along the margins of posted private property, but I believe it stays inside the WMA.