[AU-NZ] Road geometry

[petrar-telenav]

Since January we started to work on road geometry in Canberra, Perth and Melbourne and we came across some intersections where roads (turn lanes) are mapped separately even where there is no physical divider or chevron markings.

Below are two examples where you can see how the geometry is now in OSM and how we would edit: -32.0914374, 116.0129206 -35.3409195, 149.1616891

What’s your opinion about? What is the reason why turn lanes are mapped separately in these cases?

[JohanEntur]

You should probably re-do these screenshots. The size and compression makes it almost impossible to see what is going on here.

[EwenH]

Hi @JohanEntur , try clicking on the image and it should expand. I do not do much with counting lanes and how to render larger intersections.

What is the reason why turn lanes are mapped separately in these cases? I believe that the reason for this is that that poorer satellite imagery in Australia in the past did not allow armchair mappers to map turning lanes accurately and so mappers did the best they could by rendering something that was navigate-able and allowed one-ways and restrictions. This became the norm as others followed. I also think the ID editor could do more with prompting users with regard to defining lanes.

The other area was probably more priority. Years ago, multiple roads were missing and it was probably deemed more important to get these mapped rather than second guess lanes etc and that editors did not considered that detailed navigation was available.

My thoughts are

1. I see both versions of the t-intersection being correct however your version probably being more factually correct for what is on the ground although the original version may allow easier navigation.
2. If you are using lanes and defining turning lanes in the flyover image, I believe this resembles a better representation of what is on the ground and would suggest this is an improvement.

I hope this helps.

[jberkers42]

Hi @petrar-telenav,

As per Warin's and my comments on the talk-au list, there is a question about the solid white line constituting a legal boundary that cannot be crossed.

From my talk-au comment regarding the Canberra flyover:

I think the main issue is that the node where the ways diverge is a significant distance from where the line become solid. If fact, the node is near the beginning of the dashed line.

If the divergence of the ways was placed nearer to the commencement of the solid white line, this would maintain the ability to implement turn restrictions, and clean up the intersection. Lane tagging is also recommended, prior to the divergence of the ways, so that supporting navigation aids can advise the driver appropriately.

I also note that, legally, it is not permissible to drive from the off-ramps straight accross, back onto the on-ramps in this scenario. Mapping as above would avoid any confusion as to possible turns by preventing these altogether.

Hope that helps.

Regards, JohnB

[steerage250]

For the WA example, I prefer the simpler Telenav version. I prefer the simpler version for the Canberra intersection as well, but (if, as JohnB suggests above), it not permissable to drive from the off-ramp, straight across to the on-ramp, then a solution would need to be found for that.

[petrar-telenav]

Thank you all for sharing your opinions.

As a conclusion: If there are chevron marked areas or gores:

• If the intersection is already mapped, we will leave it as it is
• If we should map a case from 0, we will take them in consideration to map turn lanes separately, but just if we think it impact the routing

If there is nothing on the pavement, we will simplify the geometry as in the cases discussed.

As a note, we have in scope to map also lanes and turn lanes. @jberkers42 , thanks for your remark about not being able to go from the off-ramp directly onto the on-ramp – we will see how we could cover this with turn restrictions.

[andrewharvey]

I actively remap from the left example to the right example as this is consistent with only separating ways when there is a physical barrier. So :+1: to your proposed remapping.