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@Durango Dave
Sometimes it is hard to work out what the XT2 is doing. In this case it could be one of a number of things.
1. The road is subject to seasonal closures, or the map thinks that there is a road closure. There is very little that you can do about that situation. You frequently get that sort of problem when planning rides at this time of year for Summer tours in mountain regions.
2. The XT2 likes to use faster roads when 'faster time is selected as the routing preference. This may mean that if it is quicker to go back to reach a faster road that is heading in the right direction than it is to go forward to the next VIA point, then it takes that. It would be interesting what your route would do if you put a VIA point either side of the 'closed' section. Currently the XT2 treats shaping points very differently from the way it treats via points.
3. If you are using the Tread App, or have the XT2 synching through Tread, then there may be something going on there. Somewhere - either at the Explore/Tread database end or in the Tread app, the synch process alters the planned route, often moving shaping points onto different roads, and taking the route with it.
4. If these screen shots were taken while on a ride, then something else may be going on. I won't go into that possibility because if you are simply planning your route, it is not relevant.
5. The map may be wrong. Either deliberately or accidentally. There is nothing you can do about that except report it. On the XT2 route planner, and on the Tread app you can select the segment of route (that is the length of magenta route that is bounded by two via points) and change the routing preferences for just that segment. Eg to shorter distance, or to direct / straight line.
As an anecdote, jfheath wrote:We have a narrow steep lane which I use to get to my house at the uphill end. It is tarmacced and a legal route, but navigation is made awkward by parked cars and one short but extremely steep blind section. I could use a parallel main road, but the junction onto that is blind and dangerous. I've been using the lane for the past 40 years. The satnav hasn't complained since I first got one.
Recently, frequent road works on the main road has resulted in tailbacks, and those who know use the lane as a way of getting past the queuing traffic. The result has been many head on bumps especially on the blind, narrow steep section. The locals, whose front doors open straight onto the narrow pavement are fed up with this and tried to get the road altered. One way system, partially closed. etc. Nothing happened. Except, one day after a map update, my satnav refused to navigate me down the road.
So I investigated. A very short section of the road - maybe a couple of metres - the satnav will not plot a route from one side of the section to another. There is nothing on the map that I can see.
A little while later, I noted that Garmin are using OSM mapping. Open Source. These maps are developed by thousands of volunteers adding an incredible amount if detail to the mapping of areas around the world. And you can sign up to become a contributor. So I did.
And the only thing that I have ever done as a contributor is look to see what is plotted down this back lane. Bollardss. Someone has plotted bollards on the map. So according to the mapping I cannot navigate down that section of road.
The satnav agrees. Until I reach the 'bollards', the satnav is demanding that I go back. As soon as I pass through the non existent bollards, the satnav navigates ahead.
Since noticing that, I have observed other places where eg the satnav is reporting incorrect speed limits. They used to be correct, but now they are not, and other places where roads are apparently being rejected by the satnav as viable alternatives.
But again in this situation, put a couple of via points either side of the blockage. when you reach the blockage and the satnav is directing you to go back, just continue. The satnav will recalculate and (eventually) navigate ahead to the next via point. Other Zumos before the XT1 will do the same with shaping points. The XTs are less predictable with shaping points, and the XT2 /Tread combination seems to treat them with contempt.
Advice that you will find elsewhere:
Don't allow the Xt2 to synch with Tread.
After importing any gpx file, apply the 'fix' to make the XT2 believe that it has not been imported. Use the XT2 facility to copy a loaded route. The copy will behave itself.
Avoid using Skip. The entire route will be recalculated.