Basecamp routing 101

Former Member
Former Member

Admittedly, I am a Basecamp (version 4.8.4) newbie... be that as it may...

Can someone explain the following phenomenon in such a way that a reasonably intelligent person will understand?

I create a route from point A to point B and Basecamp calculates it according to my preferences (avoid interstates, etc.)

I then add a single waypoint to the route. Not just any waypoint, a point that is precisely along the route it has already calculated.

Upon recalculation, Basecamp now has me turn right out of my subdivision, instead of left... and I end up with with a new route that is twenty minutes longer than my original.

Can someone explain this? 

This is totally unsatisfying and frustrates the heck out of me. I cannot fathom why I would want to use software that behaves this way.

A similar thing is happening on my brand spanking new Zumo 595lm - add a point to the middle of the trip, along the calculated route, and the whole last part of the trip is completely different, with an additional time of about twenty minutes.

This seems nuts... but I will welcome a logical explanation from anyone who knows why this is happening.