I-78. Have done the drive so many times from Allentown to Harrisburg area and there is enough variety to keep me going. Whether the farmland, warehouses, that guy from New York in the left lane going 65, the lady from Virginia going 105 and doesn't matter who's what and where...still going 105, and that trucker duking it out with the other trucker on the small rolly hills...only to be full weight and cannot go uphill; makes the slower trucker catch up. It improves my driving awareness skills and I love it. Sadly, the trips to Allentown are likely going to dwindle down next year. But trips to Shartlesville will be the same.