The big problem heading north is the Merrimac River and the few rural places to cross it. I originally aimed for the Tyngsborough crossing but that wasn't feasible on the shorter ride I needed to take. Instead I made my way to the outskirts of Lowell on less traveled roads and bike paths and then crossed the river on the ancient and temporary Rourke Bridge. From there I found my way to Mammoth Road and took that towards Londonderry. Mammoth Road isn't all that well traveled but the speed limit is fast and today there was as much traffic on the road as I've ever seen, although that doesn't mean it was heavily traveled as say, Rte 2A from Lexington to Concord at 7:30 AM.
My route did take me away from Route 4 into Chelmsford, instead taking small roads and then the Bruce Freeman bike path so I can't say that my ride was all on major roads. But the second half of the ride, north of Lowell, was a far cry from the quiet roads I planned, but getting out safely and enjoying a long ride was far better than not riding my bike at all.
Miles for the ride: 45, for the month: 235, for the year: 1680.
Crossing the New Hampshire line on Mammoth Road, NH 128: