Weird Routing Behaviour (2)

[Peobody]

Coming to a stop sign, in order to go left I have to go right and in about 500 yds make a uturn to go the direction I want to. It's becoming more and more imperative to have prompted recalculation and always either say NO or just ignore it.

Indeed! This is so frustrating. These u-turns are by design, sometimes having a traffic signal that stops oncoming traffic so that u-turners can make the turn. Most are not on the map (at least not yet) which results in an off-route condition. In the example below, if I am heading north on Old Charlotte Rd SW and want to go west on Rte 49 I must turn east and then make a u-turn, (there is a barricade down the center of Rte 49). This is an intersection that is visible on the map and known for no through traffic on Old Charlotte Rd SW so BaseCamp routes accordingly, sort of. The designed u-turn spots are not recognized for what they are. In this case, making the designed u-turn keeps you on the route. Not so when this forced u-turn design is not on the map and the route attempts to take you through the intersection.

Forced u-turn.png (149.24 KiB) Viewed 2007 times

Routed forced uturn.png (266 KiB) Viewed 2007 times

[danham]

Apologies if I'm being thick about this, but I don't fully follow your example. I can see that in order to go west on 49 you have to get on 49 east and then do a u-turn. What is unclear (my fault, not yours) is what the problem is for the XT. In your example it obviously worked correctly, but you say that in other cases it would not. If the Old C/49 was one of those cases, does that mean the GPS would tell you to turn left at the intersection of Old C and 49, even though it is not physically possible to do so? If my guess is correct, does that trigger RUT? And why would having u-turns disabled make this all worse?

Thanks for helping me understand (and choose the best settings),

-dan

[Peobody]

If the Old C/49 was one of those cases, does that mean the GPS would tell you to turn left at the intersection of Old C and 49, even though it is not physically possible to do so? If my guess is correct, does that trigger RUT? And why would having u-turns disabled make this all worse?

Yes, the GPS would tell you to turn left, or go straight if that is your route. The right turn puts you in an off-route situation. If a recalc occurs, you potentially have a messed up rest of the route, likely exacerbated if u-turns are disabled. If you don't allow a recalc and just do a u-turn to get back on the route then all is well. It would not trigger the RUT issue. AFAIK, the RUT issue is only associated with skipping a point.

It is becoming surprisingly common in NC for major roads and state highways to not have any cross intersections for many miles. Instead they have periodic u-turn spots. These are not limited access roads; entrances from side streets and business parking lots are right-turn only. If you want to go left you may have to drive a couple of miles before reaching a u-turn opportunity. I would be interesting to see what a route might look in some of these areas if u-turns were disabled.

[danham]

Got it -- thanks very much. The trend in the northeast is to create "jug handle turns" -- you sort of exit right and it loops around left and puts you perpendicular to the original road, often at a light, then you turn left.

-dan

[Rofor]

@Peobody

That is definitely not my experience. It calculates a route to the next point AND recalculates the routes between all remaining points. What I am unsure about is whether it handles shaping points added with the BaseCamp Insert tool differently from shaping points created by setting a via point to non-alerting.

My answer was a bit misleading, sorry (couldn't it describe better) - i meant it exactly as you describe it above, and yes - on our findings the Zumo XT uses all shaping points for recalculation, nevertheless how they are created!

[rbentnail]

Got it -- thanks very much. The trend in the northeast is to create "jug handle turns" -- you sort of exit right and it loops around left and puts you perpendicular to the original road, often at a light, then you turn left.

-dan

I grew up in northwest NJ- we had jughandles at least as far back as the mid-'60s. I can still remember the signs- All Turns Keep Right.

[Fxwheels]

Got it -- thanks very much. The trend in the northeast is to create "jug handle turns" -- you sort of exit right and it loops around left and puts you perpendicular to the original road, often at a light, then you turn left.

-dan

I grew up in northwest NJ- we had jughandles at least as far back as the mid-'60s. I can still remember the signs- All Turns Keep Right.

Right. They still all there. I'd sure prefer roundabouts like they have many in Europe. It's much safer than a stop signs or a traffic lights. And making a u-turn is easy and fun

[Plainmad]

This is an interesting article that mentions issues with the XT.
Two identical ones with identical box files but trying to take different routes

https://fliesonthevisor.com/three-days- ... -the-road/

[Peobody]

That was an interesting read. Two XT's configured the same, routing differently from the same .gpx file. Yup, they are XT's all right!

[jfheath]

I'm not surprised by that behaviour.

Apart from the various ways in which the route may have been altered by Basecamp (by loading into a profile with different preferences, by having different maps, etc); on transfer to the XT (eg different Basecamp Settings, different maps); by the XT on loading or starting off, there are plenty of other factors.

The XTs can load a route and then apply the route preferences stored in the individual XT. They can build up a profile of the rider's style of riding, speeds, type of roads, preferred routes. Unless you can control all of the alternatives, every step of the way, two XTs are very likely to come up with different routes.