The southern terminus of NH 155 is in Epping at the junction with
NH 125 (Calef Highway). Just to the north, the highway crosses the county line into Strafford County and the town of
Lee, crossing
NH 152 along the way. NH 155 travels through the center of Lee. A few miles later NH 155A splits off eastward into Durham while NH 155 turns northward towards Dover. Continuing north, NH 155 meets
U.S. Route 4 at a half-
diamond interchange, limiting access to two movements: US 4 eastbound to NH 155 and NH 155 to US 4 westbound. Access to US 4 eastbound is facilitated by nearby NH 155A, which rejoins its parent and runs east (signed south) to its own interchange with US 4. NH 155 continues north along the western edge of
Durham and the eastern part of
Madbury before crossing into the city of
Dover. The highway continues north for another couple of miles before reaching
NH 9, less than from the
Spaulding Turnpike exit 8 interchange. The roadway continues as NH 9 eastbound towards downtown Dover. ==Major intersections==