I love this site, and it offers the best routes of any I have experimented with. I just used it to map and then follow a 120 mile cross-country route from Cambridge to Evesham. But there were a couple of points where the cycle.travel suggested route deviated from the NCN route it had otherwise been following. One of them was actually quite nasty and dangerous: in Bedford, the Cycle.Travel app routed me across a really nasty junction onto the main road out of town whereas the NCN route continued for maybe half a mile along the river before crossing back to the same road.
I imagine this is because there is a misleadingly labelled section of bike path along the main road in the underlying OSM/OpenCycle map. It's actually a lumpy shared use pavement and to reach it you must cross four lanes of traffic (at lights, but still).
Is there some way to feed into this site/algorithm a note to avoid specific junctions like that one, or should I try to edit OSM in some way to warn others?