Hi
Absolutely nothing to do with camping in NH (off topic on the third post .... maybe a record ...). Coming from Texas to New England, there is an interesting "feature" you will encounter. The polite name for them is toll roads. There are many other more descriptive terms.
Tossing coins in hoppers or handing over large wads of bills every 10 miles gets boring in a hurry. Slowing down to zero and accelerating back up to speed does not help MPG. Most of the roads accept an EzPass. Yes, it costs a bit ($35??) to get the transponder. Part of that is the deposit for your first round of tolls (You *will* spend it ...). The advantage is that you can go through the "express lane". That gets you past the toll booths and lets you stay at cursing speed. The other advantage is that the tolls are (in general) cheaper if paid by EzPass.
Indeed you *can* avoid the toll roads. You will see a lot of "interesting" small roads and small towns. You will have a bit more trouble avoiding the toll bridges.
Sorry for the veer off into the weeds ....
Bob