Missing turn instruction when turning but on same road

[MotoUKRider]

This stems from a post about observations in Cruiser (Desktop, online BRouter) vs Cruiser App (offline BRouter).

Where a road type continues but requires a turn (slight or otherwise), there is no turn instruction (or turn "blobs") within Cruiser App.

Here is an example route from the Isle of Man with a road requiring a "slight turn" - also verified using Google Street View.

In this image (local to me, so detail removed), you must turn to stay on the "Primary" road as you approach from the right. If you miss the right turn, it becomes a "Secondary". So, in this scenario, if your phone is in your pocket and you're relying on spoken instructions, there wouldn't be one!

This seems to boil down to either a difference in the online-vs-offline BRouter and perhaps the "drawing" of roads within OpenStreetMap and some kind of turn threshold in the routing algorithm.

[devemux86]

@afischerdev

• Testing on BRouter website the instruction exists

• Testing on BRouter test website or latest BRouter app the instruction does not exist

• On websites we use the export's middle "cloud" button to get the GPX navtrack or GeoJSON files

As the main BRouter website uses old BRouter code,
probably some of the recent code changes removed such turn instructions?

[afischerdev]

Thanks for the example. Very helpful.
I think I found the reason. But as always it changes lots of older results.
Here a small collection: first old than new output

At the end it doesn't look to bad to me.

[MotoUKRider]

Interesting... There is clearly a lot of if/else/or/but/except at work here!

Within Cruiser App, I just tried another route local to me with 2 "missing" BRouter turns (including the screenshot in my opening post) with online GraphHopper+OpenRouteService which both produce the turn instruction (as does GoogleMaps).

Interestingly, OSRM+Valhalla both produce a further instruction mid-route when there is a 90-degree left-hand bend (same road, just a sharp ~10mph corner) - perhaps the "service_road" off to the right has a bearing on this? The segments in OSM are co-incidentally right at the "turn" marker!

What is concerning is that when approaching a tee-junction, there is no turn instruction - possibly due to how the road is "drawn" in OSM? I'm not sure. This obviously raises the issue of voice-only navigation only telling you that there is a problem when you're 100yrds down the wrong road!

Example: I have added a red line to show the give way point - so traffic flows from the top and round to the left (into a village). Approaching from the right, you must give way to traffic coming out of the village or from the top.

[afischerdev]

@MotoUKRider
I don't know where your junctions are.
Here is a similar situation - I think.

I this example the left turn has a voice hint.
Testable on test server now.

Note: in old version both routes have no voice hint.

[MotoUKRider]

@afischerdev Looking at your example (in Cruiser App) does not produce a "turn left" instruction, but on Google StreetView, it is merely following the road round to the left. There is a "give way" line+sign coming from the left - so although it's a 90-degree bend, there's no turn.

I would class a "turn" as where you are required to give way to opposing traffic.

[MotoUKRider]

Here's a good example to experiment with: this crossroads on the Isle of Man.

Using the Trunk road, making a left (A18 to A3) or right turn (A3 to A18) - no turn instruction (a problem)
Straight over in either direction, no instruction (correct, IMHO)

[devemux86]

More instructions for "turns" are useful when navigating with only voice guidance and without a screen.

So, it is better to have more instructions for "turns".

We should avoid unnecessary "continue straight" instructions.

[afischerdev]

@devemux86
Yes, you are right. That's what I'm looking for at the moment.

The first example above (driving right to left, nn voice hint) could be a candidate for avoid straight. There is no crossing traffic when going straight.
But these examples have the crossing and no voice hint:

@MotoUKRider
Back to Isle of Man. The problems are the same. Coming from South, going left (West) produce a voice hint left now. But in both directions (from top to bottom, from bottom to top) there is no voice hint.

Note: All examples are done with the first correction voice hint generation. More is needed - I think.

[MotoUKRider]

@afischerdev I think the requirement of a turn/voice hint should boil-down to a few (hopefully simple) parameters:

• Am I at a crossroads where I do not have priority? (ie: I have to give way to traffic from the sides) Only if turning left/right
• Am I at a crossroads where I do have priority? (ie: where traffic from the sides must give way to me) No
  (the same scenario would apply for any left or right side-roads, as they are irrelevant to the journey)
• Is this junction a "tee", so a left/right instruction is vital (especially if the road continues to be the same name/ref) Yes
  (this is where I've found a few issues due to how the road is drawn in OSM. It looks like a bend, but is a junction)
  Here's another great example, central UK - verified in StreetView as a "Give Way" but appears as though it's a bend. At present, Cruiser App does not produce a turn instruction when turning right, staying on the A612.
• Is this a controlled crossroads where the road continues left/right? Yes
• Does the road naturally curve with other roads joining it (like in your German example) ? No

I would say that the key takeaway here is to avoid the scenario where a missing instruction would result in going off-route!

[afischerdev]

More on the examples from Britain.
All is testable on test server, I installed a new temporary library.

The critical junctions hava a voice hint, the other intersections passed do not.

@MotoUKRider

Am I at a crossroads where I do not have priority? (ie: I have to give way to traffic from the sides) Only if turning left/right

I do not agree. In my eyes crossing a higher priority street needs a voice hint.

[MotoUKRider]

@afischerdev Thanks for this - upon reflection, I agree about the crossroads; a "continue/keep straight" sounds logical.

I'll dig deeper into the test server, too. At present, I am using Cruiser App to plot routes finding "odd" junctions (because searching a map at a close-in zoom is not enjoyable) and then comparing them to Cruiser Desktop (which uses "online BRouter") and then I can try them on your test server.

Hopefully this fixes a few navigation issues going forward 🤡

[MotoUKRider]

@afischerdev Thanks for the fixes - in the latest Cruiser App from @devemux86 I can see a few examples where a turn instruction is now issued.

Interestingly, if I reverse a route (in Cruiser), a turn instruction may (dis)appear. This central UK location, the junction from earlier in the thread, travelling up and turning right does not produce a turn (which is odd because I'm at a "tee", so must turn!). If I reverse the route then I get a "turn left" instruction.

You'll prefer a small-size map example too, I guess! A similar situation exists on the A26 Isle of Man. Flipping the route removes the turn. The junction layout is odd, but I wonder if the behaviour is intended - particularly where the "turn" keeps you on the same road name/ref but does not follow the physical road layout.

[afischerdev]

@MotoUKRider
I'm not sure, this is not intended. Found this comment:

ways from the back should not trigger a slight turn

[MotoUKRider]

@afischerdev In the Isle of Man example, the 2nd image showing the route heading south, I arrive at that junction which is a "STOP" (ie: must stop and give way). The layout of the crossroads is angled/staggered (hence the safety aspect of the "Stop" sign) according to StreetView, but even if continuing on the same road ref, when there is a decision to make - I think a turn instruction should occur.

This kind of "to turn or not to turn" can also help/relate to a simple "itinerary", or what I call "TankBag Navigation" where each turn is listed along with the distance to each one. I know road signs are a thing but it seems that, with my road layout examples, it's quite easy to ride past a turning and/or have it missing from the route instructions.

This is a good location to experiment with: Angled/staggered crossroads with the "Primary" road not continuing on the physical layout of the road: