Location is tricky....
BITD when Avocet cycling computers came on the scene we used the Buxton - Leek road to see if we could hit it's max speed.
This section to be more precise: https://www.strava.com/segments/649653
When I look back it was utter lunacy considering the traffic and motorists attempting to overtake having little to no comprehension of what speed a bike can go; arguably more dangerous than the mountain passes I've been over in the Alps and Pyrenees.
If you can find a closed section it will take a massive chunk of danger away from the equation.