Thanks for the answer. I already took a look at google maps and they do acutally offer something called "Distance Matrix API". The only problem with it is that the API key costs money.
What's an API?
https://xkcd.com/1481/ applies.
In this particular context, do you mean "getting the technical info costs money?" or "I need to buy account on their mainframe (for want of a better word) before I can do anything clever".
Elsewhere, somebody's suggested using Google Earth for this. However I don't recall Earth being aware of roads or similar entities which can constrain a route such that it's not a mere "as the crow flies" guess.
I'd add though that there's a great deal of useful stuff buried inside Earth: it was actually a fairly competent piece of GIS software before Google bought it up and bent it to their unholy will. And looked at from the other side, QGIS (as one specific example) can get overlays from Google and others... but again I don't know whether that has the concept of following roads.
MarkMLl