Confused! I don't want to randomly autoroute. If I have enough defined waypoints will that nail it down?
Nearly always yes, for extremely variable values of 'enough'. Therein lies the rub. Every now and then you come across some section of road that the algorithm will - for no obvious reason - go to extreme lengths to avoid. Usually you can lay down enough routepoints to persuade it, but there are occasional exceptions.
Similarly, auto-routing is much more sensitive to gaps in the map. If a section of road is missing (eg, because it's technically two dead-end roads joined by a footpath, or a road that's just randomly absent from the map), you can hand-wave over it in an off-road Route or Track, as they're not tied to the map. But auto-routing has no allowance for that sort of thing. You can bung a routepoint at your dead end, and another on the other side, but you can't stop it from leading you round the houses to get from one to the other. My preferred approach is to add a waypoint (with proximity alarm if needed) reminding me to ignore the auto-routing for a bit.
The pragmatic approach to using auto-routing for audax type rides is to back it up with a visible Track. That way you get the convenience of reminder beeps and highly visible instructions, but if it does something suspicious (eg. leading you downhill
) you have an easy way to quickly confirm whether or not it's talking bollocks.
I appreciate that it's a hard problem, but it shouldn't be this hard.