#15 north of Harrisburg PA?

It is doable but is a congested area. I don't recall any narrow places but your biggest issue will probably be dodging all of the cross traffic....

If you want to make it easier, get on I-81 south at Enola, go to 581 and the get back on 15 south at Camp Hill. You'll still get some two lane and cross traffic but that will get your around a bunch of it.

We often go that way but since we are on our way to Carlisle we don't go south of the I-81 entrance. That piece from Marysville to 81 is slow, a little narrow and has one rather tight turn but we enjoy the ride and the scenery before we get back onto the craziness of the interstate. We do it with a 29' travel trailer and an F-250. Just watch the speed limit, keep your distance, and enjoy the scenery.

Avoid morning work traffic if possible, otherwise you should have no problem. And when you do get to I-81 S take that to 581 which loops around back to 15 S. Longer but keeps you out of some tight and congested areas.

Third time is a charm. Agree and strongly recommend the others who say to take I-81 West to 581 and back to RT15 S that way. Much better roadways which are wider. The intersections of 581 & 15 USED to be very bad, but have been redesigned, and rebuilt making for an easier merge. I have a 35 ft TT and went 15 thru Harrisburg ONE time...Never again! I always use 15-581-81-15 going North and the opposite on my return.