Mini_roundabout

[Casey_boy]

@Peter_Elderson

Someone said the legality of that is questionnable?

In the UK, it is not illegal to perform a u-turn at a mini-roundabout (unless also signed with a no u-turn sign) . It is, however, advised against:

Rule 188
Mini-roundabouts. Approach these in the same way as normal roundabouts. All vehicles MUST pass round the central markings except large vehicles which are physically incapable of doing so. Remember, there is less space to manoeuvre and less time to signal. Avoid making U-turns at mini-roundabouts. Beware of others doing this.

For clarity, only things listed as MUST (or MUST NOT) are legal requirements. So the “avoid” part is just a recommendation:

Many of the rules in the Code are legal requirements, and if you disobey these rules you are committing a criminal offence. You may be fined, given penalty points on your licence or be disqualified from driving. In the most serious cases you may be sent to prison. Such rules are identified by the use of the words ‘MUST/MUST NOT’. In addition, the rule includes an abbreviated reference to the legislation which creates the offence. See an explanation of the abbreviations.

Although failure to comply with the other rules of the Code will not, in itself, cause a person to be prosecuted, The Highway Code may be used in evidence in any court proceedings under the Traffic Acts (see The road user and the law) to establish liability. This includes rules which use advisory wording such as ‘should/should not’ or ‘do/do not’.

But, regardless of strict legality, we wouldn’t want a router advising a u-turn at a mini-roundabout because it is not advised - even if it is not illegal.

Further to all of this, this is just for the UK. Legality may vary across other countries.

[Yunkers]

@Peter_Elderson

What’s wrong with them? I mapped a zillion turbo roundabouts, so I would like to know!

Generally I’m using Magic Earth as routing and it has difficulties with showing the correct lanes on those. So instead of showing that you need to use left lane, it shows right for example. It happens in big roundabouts with multiple lanes too. (Or at least, it used to happen, I haven’t check for a while)

[Peter_Elderson]

Turbo roundabouts can’t cause wrong lanes, because wrong lanes do not connect to the destination!
On multi-lane roundabouts I can imagine this to happen, but the standard turbo-roundabout does not have multiple lanes.
If this error happens, the result would be that the router takes the wrong exit, and has to reroute or make a U-turn somewhere else. This does not happen with the three demo routers on osm.org. Do you have an example?

[Yunkers]

Osm routers do not show turn:lanes at all, so couldn’t show there I’m afraid. I’ll chrck if I can find an example from the app, in free time.

Edit: Weirdly I have checked Magic Earth and the turbo roundabouts seem to work correcltly. I’m not keeping up with technology

[Peter_Elderson]

@Casey_boy

But, regardless of strict legality, we wouldn’t want a router advising a u-turn at a mini-roundabout because it is not advised - even if it is not illegal.

Hard to map for “not advised”. But I agree: it would be good that routers/navigators can ‘see’ that the roundabout is of the mini-variety. Just as they should get the information that a roundabout is of the turbo-variety, so the announcements and navigation directions can announce that you’re approaching a turbo roundabout, and suppress the confusing exit count.

[trigpoint]

They are not the same as rond-points, which is where priority is to traffic joining. These are now very rare.

Mini-roundabouts are a painted circle with priority from the left, with standard give way signs, rather than the blue circulation sign we have in the UK. Will pay more attention to the signs next time I see one.

[Casey_boy]

@trigpoint

Mini-roundabouts…with standard give way signs, rather than the blue circulation sign we have in the UK.

Mini-roundabout has the blue sign you’re talking about whilst roundabouts have the red warning triangle.

Mini-roundabout: Mini-roundabout (roundabout circulation - give way to vehicles from the immediate right) road sign | UK Traffic and Road Signs
Roundabout: Roundabout road sign | UK Traffic and Road Signs

Or here for all signs: https://assets.publishing.service.gov.uk/media/58170307ed915d61c5000000/the-highway-code-traffic-signs.pdf

[Casey_boy]

@Peter_Elderson

Hard to map for “not advised”.

I don’t think we need to map it. Mapping as a mini-roundabout is enough. It’s then for the routers to understand local traffic laws and guidelines.

I think it’s just a case of deciding:

• Should we “allow” mapping of mini-roundabouts as ways (rather than nodes)?
• If so, what tagging do we use (i.e., junction=mini-roundabout or junction=roundabout + roundabout=mini both have pros/cons)?

[SekeRob]

@Casey_boy

… whilst roundabouts have the red warning triangle.

Thought we were rather uniform in the EU, but here in Italy this is a pre sign ‘roundabout coming up’, usually at the standard distance of 150m BEFORE. traffic sign code IT:A22. If not at 150M there’s a sub sign to indicate the distance.

At the roundabout the yield sign and the roundabout sign usually a few meters prior to the shark teeth painted on the road where you have to wait for traffic on the roundabout to pass.

[trigpoint]

Organic maps renders mini-roundabouts as ways and gives roundabout style exit numbers, so all of the issues here seem to be rendering issues with some routers.

[Peter_Elderson]

@trigpoint

Mini-roundabouts are a painted circle with priority from the left, with standard give way signs

With only warning signs at a distance, as I have seen in France, there is nothing at the junction to force the oneway circular traffic. Seems strange. In Nederland, lots of juncions have painted/raised/differently paved circles or dots in the middle, but without the roundabout traffic sign it’s simply not a roundabout, and there is no mandatory circulation on the junction, and there is only the default “right first, including bicycles” priority rule. Many are too small to even think of driving in a circle. If the centre point was a concrete block, most 4W vehicles couldn’t pass.

[Peter_Elderson]

@trigpoint

Organic maps renders mini-roundabouts as ways and gives roundabout style exit numbers, so all of the issues here seem to be rendering issues with some routers.

Well, rendering a dot as a circle doesn’t seem that hard, provided that the information is present in the data. With a standard mini-roundabout without split roads counting exits also seems pretty straightforward. Though I heard someone say that drivers prefer regular junction style navigation instructions (turn left, instead of take the third exit).

[rmikke (Ryszard Mikke)]

@Peter_Elderson

Mapping a roundabout with cut-up ways: how would a tool know what to do with ways, nodes, splitting, geometry?

Create a circle then split it into separate ways at where the roads join? After that, adding to the relation fragments from where the relation enter up to the joint it exits the roundabout? Assuming the relation is ordered…

[Peter_Elderson]

@rmikke

Create a circle then split it into separate ways at where the roads join? After that, adding to the relation fragments from where the relation enter up to the joint it exits the roundabout? Assuming the relation is ordered…

How would a tool know the required geometry? Would it split the roads into approach and exit ways, aasuming there are flare islands? If not, who will do that? “Where he roads join”, those junction nodes will have to be created, right? Will the tool do that?

By hand, it is not that hard. I assume there are flare islands separating the approach from the exit, for each road, but that the roads are now represented by one way each, ignoring the flare islands, ending at the highway=mini_roundabout junction point.

First thing I would do is split approaches from exits, by adding a node to the way near the flare, cut the way, then copy the last section, attach one end to the split point, and move the other end to the position where the circle wil be. Then add oneway=yes and reverse the direction where necessary.
For all the roads.
Then I would draw the circle, using enough nodes, in the intended direction, ie clockwise for the UK, attaching existing road segments and the new ways created in step 1. Usually the shape would be round, so use O. Add junction=roundabout (implies oneway=yes) and roundabout=mini (implies that the centre island/dot/circle can be run over and that U-turns are unwanted).

Then, if there are routes running over the roundabout, split the circle at all the junction nodes.

Then delete the old centre node. This will remove the ‘spokes’.

Now the route relations can be fixed. In JOSM, I would select (with control-click) the unsplit roads outside the junction area. Now in the tags panel, I doubleclick each of the relations listed there; each one will open in its own relation editor window, showing the gap, and also possibly way segment that should be removed.
The "select this relation’ button will show the problem nicely on the map, making clear which members should be removed (do it!) and which ways whould be added (do it!) to fill the gap according to how the vehicle should move on the junction. Save/close this one; repeat until all are done.

Yes, lots of actions, a tool would be nice, but can it replace the work? Just putting a circle in is not going to help much, I’m afraid. Then again, some of the tools such as the PolygonCutOut plugin do amazing work!

[SekeRob]

Was mentioned recently, a roundabout drawing JOSM plugin. Select the central positioned crossing node and start hitting ctrl+shft+R, first step a mini, second step ring, next steps the entrance exit flares. Not seen it do the giveway spots but it certainly is a quick result. Not tested on a crossing with route relations which is the most finicky part as are the turn restrictions around the flares.

Edit: The plugin is called Roundabout Expander

[Peter_Elderson]

@SekeRob

Edit: The plugin is called Roundabout Expander

In JOSM it’s called rex, I took a quick peek. It give a nice beginning; after that, you still have to refine the geometry (some connections may look strange, especially of the roads had nodes which fall within the created ring) , and if there are routes you need to cut up the ring yourself and repair the routes.
And then extras such as yield signs, excusez, give way signs and turn restrictions. As with any roundabout, a flare turn restriction is appropriate if there is a continous line between the two direction on a road.

[Peter_Elderson]

I looked at the Magic Roundabout today, to see what rex would make of that, and to my surprise it now looks like this:

The inner ring (counterclockwise traffic) is tagged junction=circular. The miniroundabouts are not mapped as mini-roundabouts any more, just oneway roads. Priority is mapped only as give_way nodes.
Did a bit of testing, looks like the routing works, though I don’t think it will help you choose the best lane.

The routes have not been repaired, I think.

[rmikke (Ryszard Mikke)]

@Peter_Elderson

How would a tool know the required geometry? Would it split the roads into approach and exit ways, aasuming there are flare islands? If not, who will do that? “Where he roads join”, those junction nodes will have to be created, right? Will the tool do that?

By hand, it is not that hard. I assume there are flare islands separating the approach from the exit, for each road, but that the roads are now represented by one way each, ignoring the flare islands, ending at the highway=mini_roundabout junction point.

I haven’t thought of adding flare islands automatically. We don’t need them for fixing relations. After all, the same node may be entry point for one relation and exit point for another. Why not.

OTOH, the tool could be able to add such a flare island and fix relations again. Would be useful as regular roundabouts often do have them.

As for geometry - of course it would need manual correction, unless someone writes some AI engine fitting the geometry to existing imagery and taking possible offset into account . But most of the technical job would be done and moving nodes wouldn’t break relations.

[Peter_Elderson]

@rmikke

OTOH, the tool could be able to add such a flare island and fix relations again. Would be useful as regular roundabouts often do have them.

I would not consider upgrading the mini-roundabout to a small roundabout if it didn’t have at least one physical flare island. I don’t know the traffic habits in the UK, but here, when there is a junction of non-divided roads, and two opposing drivers both want to turn left, they do not go around each other. If they did, and there were more cars behind, you would have a hockeystick hook situation. A dot in the middle won’t force the drivers to go around. They would simply see that as a nice divider, for safety.

[Mammi71]

@Peter_Elderson

A dot in the middle won’t force the drivers to go around.

in this case it isn’t a mini-roundabout