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Hello all,

An elementary BC question has been in my mind for some time, so I have decided to expose it and find the answer.

Scenario:
- I create a new two-point route in BC with just START and END, no Vias or Shapers between, a magenta route appears on the map.
- The magenta route is the route I wish to travel and I load it onto my XT.

Question: is it guaranteed that the XT will accept the magenta BC Route and follow it faithfully?
Is there greater risk of change to the Route with increasing length of Route?

Thank you,
Mikey.

Mikey wrote: ↑Thu Mar 13, 2025 1:36 am Question: is it guaranteed that the XT will accept the magenta BC Route and follow it faithfully?

No. The XT will calculate it on import unless the map is the same in Basecamp and the XT, and the XT does not have any issues with the options (eg: avoidances) selected in Basecamp. Mine calculate about 40% of the time. That's mute though because even if the XT accepts the route as is, there are circumstances that will trigger a recalculation that you can't control. Not having any interim Via points removes one of them, which is a recalculation triggered by having to skip a Via point. Another is a road closure. If the XT detects one, it may automatically recalculate the route around the closure. These recalculations affect the entire remainder of the route. Your goal needs to be to do everything you can to insure that if a route recalculates, that the resulting calculation will be on the roads you want to ride. I consider myself a capable Basecamp user but I'm lousy at outthinking the XT. If you have not learned the trick of showing a track of the route on the map, it is a valuable one. Basically, once you are done with the route in Basecamp, you have Basecamp create a track of the route. You transfer both to the XT. In the XT, there is a way to load the track so that it shows on the map as a static route line in a color of you choosing. When you then ride the route, the magenta route line should be on top of the track line, making it invisible. If the route gets recalculated, any changes will be visible because the two lines will diverge. You then can decide whether to follow the new route, manually navigate along the track line, or stop and restart the route.

Mikey wrote: ↑Thu Mar 13, 2025 1:36 am Is there greater risk of change to the Route with increasing length of Route?

Not necessarily. The XT has a strong preference for faster roads, going so far as to route you well out of your way just to travel on a faster road. Basecamp does not have that proclivity. So, it really depends on the route, the roads it travels on, and, in the event of a calculation, whether the XT thinks there are faster roads available. "Faster" only applies to the road itself. It feels like there is very little consideration given to any added time and distance to get you on that road.

Excellent response @Peobody.

Saved routes (created on XT screen) are better behaved than imported routes (from gpx files). You can make the XT think that an imported route is a saved route. Link needed.

To try to outwit the XT faster road issue.

I have a notion - (like a theory but less well formed):

When deciding how to get to the next route point (via or shaping) there are two option. One is to take the most direct route. One is to head towards a nearby faster road.

If it can reach the faster road quicker than it can reach the next route point, it will head for the faster road.

So one tactic is to always make sure that you have a shaping point that makes the faster route a poor option.

Example. A motorway between junctions 21 and 22. Takes 20 minutes
The old main road runs parallel ish, but meanders about a bit. 24 miles. Takes 40 minutes.

Put a single shaping point on the old main road to force the route to stay on the old main road and the XT will likely visit the shaping point and then turn back to the motorway junction 21 and use the motorway to reach junction 22.

Try to prevent that by moving the shaping point further away from Jn 21, and it will use the motorway first, exit at jn 22, visit the shaping point and go back to Jn 22.

But if you put two shaping points on the old main road roughly equally spaced at 8 miles and 16 miles At no point can it get to the motorway faster than heading direct to the next route point.

Result - it stays in the old main road.

Only a notion. I haven't even attempted to prove it. But having that idea in mind helps me to plot routes for the XT1 that are followed (almost) precisely.

Thank you Peobody and jfheath for your posts above.

It is quite remarkable; the measures trip preparers have to take to minimise unwanted 'control' by the XT - XT, the 'ultimate authority'!

Thankfully, it appears that with knowledge of special 'tricks', trips can be prepared that are mostly successful. I keep learning.

Thanks again,
Mikey

My takeaway from the Peobody and jfh posts above is;
an abundance of well place shaping points is a solid defence against unintended route modification by the XT.
Thanks, Mikey.

Mikey wrote: ↑Thu Mar 13, 2025 9:40 am
minimise unwanted 'control' by the XT - XT, the 'ultimate authority'!

another option is in Basecamp just create Waypoints (with no route, just waypoints) and when the waypoints are on your XT, it will calculate its own route, and if you go off that route, the XT will recalculate, giving you options and ultimate control on which roads you decide to take, giving you the control instead of the XT having control. (just a thought)

Mikey wrote: ↑Thu Mar 13, 2025 11:31 am an abundance of well place shaping points is a solid defence against unintended route modification by the XT

Doing that is my nemesis. What I consider "well placed" is fairly effective but not what I consider "solid". I don't think human logic can defeat the XT logic. An example is a route I recently created in Basecamp that avoided a historic small town center. The route was along a state highway that went to the center of town then turned left. My Basecamp route took a diagonal road to avoid the town. The XT calculation routed along the state highway through the town even though that stretch was mostly 20 mph with numerous traffic signals. I don't know if any of us can anticipate that kind of logic. You can't win 100% of the time. You just create the best game plan you can and then use contingencies to recover in the event of a knockdown.

Mikey wrote: ↑Thu Mar 13, 2025 11:31 am My takeaway from the Peobody and jfh posts above is;
an abundance of well place shaping points is a solid defence against unintended route modification by the XT.
Thanks, Mikey.

Yes - 'well placed' is preferable to an 'abundance'. You certainly need more than you would if you were using a Zumo 590 or 595. But you do not need to 'lace it up' like a pair of high boots.