When we start staring at maps for clues about old Trade Routes, especially ones that go in straight lines, it’s very easy for wishful thinking to set in, and we start clutching at straws. Look, that phonebox is on the line!
So the kind of qualitative questions that bother us are:
- how wide can a line be?
- what kind of places are cause and what kind are effect?
- why are so many old-places in the West and why are there a lot less in the East?
For example, if the line is 10m wide the degree of precision becomes extraordinarily demanding. If it's 10Km wide, et voila, it's a sweeping brush that covers everything in its path. (Cue arguments about how wide the line can be to be statistically valid)