Making changes to a BC route on a Zumo XT

[Oop North John]

However, thinking about the Route I modified on the XT and rode, the route was not a good route for a test. The first 40km is motorway, the next 50km is winding road across a range. There are few/nil parallel or alternative roads (none faster), so I expect the XT, try as it might, was limited in its scope for changing the route. I will try another time.

In my experience the faster roads problem showed the worst when it calculated that this was the "fastest" to go along two legs of a triangle ie < and the two legs were main roads. Across the legs of the < there was a minor road. Almost as soon as I went onto the minor road, the XT correctly worked out it was much quicker to use the minor road.

The 396, XT and XT2 all have the faster roads problem, so if I'm calculating a route on the unit I always zoom in to see if there might be a "better" way. The 590 and before didn't need this extra help or as many shaping points in a route. Progress isn't always forwards!

[jfheath]

I have a theory. Or a notion. Yet to be proved.

When calculating the route the Zumo is trying to get to the next route point.

Rather than calculating two or three alternative routes and choosing the fastest, which is a lot of processing time - I think that it takes the easier option of two:

1. If there is a suitable faster road that is closer than the next route point, then head towards the faster road first and then to the route poinr

2 Take the fastest route from current position.

This is from observation only, often seems to use the first method - even if it means heading off the direct route at 90 degrees and results in a route that takes much more time. I've not observed anything to disprove it - but I haven't really tried. First you have to know what it regards as a faster road.

[Peobody]

This is from observation only, it does the first method - even if it means heading off the direct route at 90 degrees and results in a route that takes much more time. I've not observed anything to disprove it - but I haven't really tried. First you have to know what it regards as a faster road.

I don't think there is any doubt that this is the behaviour, although 'knowing' what it regards as a faster road is not always obvious. Most of the time it is, but sometimes its choice to route along a slower road seems illogical.

These satnavs work great for folks who specify points A, B, and C, and then let the device route them to each point, but hey present challenges to those of us who try to control the roads on which we ride.

[lkraus]

I've seen my XT (Driving mode, avoiding only U-turns & dirt roads, Faster Time) ignore several routing options with all 45-65 mph roads, in favor of a longer route through a town with congested 25-35 mph streets, more stop signs and a long traffic light.

Inspect an XT-calculated route carefully before accepting it.

[jfheath]

I've seen my XT (Driving mode, avoiding only U-turns & dirt roads, Faster Time) ignore several routing options with all 45-65 mph roads, in favor of a longer route through a town with congested 25-35 mph streets, more stop signs and a long traffic light.

Inspect an XT-calculated route carefully before accepting it.

This is not a question, it is a thought. Me thinking out loud. An "I wonder if .... "

Is it possible that behaviour is affected by your own riding history ? I know it builds up a riding history (you can see some if it in the System Diagnostic menus), and I know that it uses it when suggesting routes. I wondered if your riding history has included going through towns - eg having the Zumo on when commuting, or having to ride through town to get home.

[lkraus]

Frankly, thanks in part to the questions posed on this forum, I probably spend more time with the XT at my desk than I do riding. With frequent resets, I doubt the XT has been able to discover any habits. I was returning from an errand and the XT actually avoided the shorter, quicker route it used to reach the store. I do not commute, most of my riding is on the rural back roads of southeast Ohio, where I avoid towns if possible. Maybe the lack of history contributes to the problem?

[Peobody]

Maybe the lack of history contributes to the problem?

I don't think so. My riding is much like that of @lkraus, only I'm on the rural roads of North Carolina. Like him, I also avoid small towns more often than not so being routed East then South through a small town with its 20 mph downtown area at the intersection was surprising considering there was a diagonal road that cut the corner and avoided the town. This is the road Basecamp routed on but a recalc by the XT routed through the town instead. The only logic that I can see is that it followed the numbered state highway ignoring that it ran through the town at 20 mph.

[lkraus]

The only logic that I can see is that it followed the numbered state highway ignoring that it ran through the town at 20 mph.

I've noticed this "logic" also. A numbered highway is often preferred to a named road, a two-digit numbered route is preferred to a three-digit route, even if the result is longer and has the same or lower speed limits.

[jfheath]

Frankly, thanks in part to the questions posed on this forum, I probably spend more time with the XT at my desk than I do riding. With frequent resets, I doubt the XT has been able to discover any habits. I was returning from an errand and the XT actually avoided the shorter, quicker route it used to reach the store. I do not commute, most of my riding is on the rural back roads of southeast Ohio, where I avoid towns if possible. Maybe the lack of history contributes to the problem?

I wouldn't know. I have reset my Xt2 back to factory condition so many times recently, that I hardly have any history either.