how I believed how it worked is that it takes your 2 destinations and mackles it together with other peoples routes most used and gives you the best route according to your desire .
I don't think CT gives much weight to popularity of route at all. If it did, we'd all be cycling the roads the local peleton rides.
It uses a variety of criteria to pre-prepare routes then pulls those together when we make a request.
(Subscribers have a greater choice of maps and some of those will show most or all the dedicated bike routes or paths in a region).
I believe its main criteria are for quiet roads (or dedicated bike path) then climbing (it likes to minimise it), then surface and believe it or not, scenery!
We really have very few (automatic) choices - paved, gravel, all (both) and lately night (especially for urban UK riding). There is a brand new option to follow "official" bike routes for more long distance rides. However, we can easily add viapoints to change the CT suggestions to suit ourselves. My understanding is that some category of rider don't like CT's automatic routes, preferring direct over meandering and attacking climbs as opposed to avoiding them.
There are a few quirks. For example, a desire to avoid busy roads can see us being dragged off a main road for a km or two only to rejoin it and then be directed off again. Similarly, CT can have a tendency to bypass towns (more traffic), something especially noticeable in NL.
Another quirk is that it rarely chooses to automatically follow an official bike route (although we can now tell it to do just that). That's because CT's own calculations offer a "better" experience than the planners of the routes. In my experience CT is correct.
Any online planner depends on the quality of the underlying data and sometimes that data can be dubious so we should never depend 100% on any planner. In my experience, CT does a better, more reliable job than most others.
