Is it Acceptable to Map a Roundabout Incorrectly?

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Is it Acceptable to Map a Roundabout Incorrectly?

Postby AndyPot2 » Wed Jun 25, 2014 6:00 pm

I suspect this may be divisive but I'm looking for guidance / opinions from other editors. I'm wondering if it would be acceptable to map a roundabout incorrectly to make it appear to map correctly for the majority of users :roll:

There is a UR here on the A404 which is a major dual carriageway linking the M40 with the M4, it's a road I (and I suspect a number of other editors) know well. The problem is this roundabout has 5 exits however all the road signs only show four exits. The road signs do not show a small dead end road called Under the Wood that serves a few houses.

Bisham Roundabout.JPG
Bisham Roundabout Road sign
Bisham Roundabout.JPG (24.35 KiB) Viewed 944 times


Under the Wood should be shown at the 7 o'clock position on the road sign therefore if approaching the roundabout heading towards the M4 ie staying on the A404, Waze will prompt you to take the third exit, if you follow the road sign (and why wouldn't you it's 20 foot high) you will end up turning right towards Marlow. Although I live locally and use this road a lot I had never noticed the extra exit but looking on street view it's quite obvious. I suppose in mitigation you look at that road sign and then as you approach the roundabout you are looking right trying to spot a gap, the Under the Wood exit is then out of your line of sight.

UndertheWood.JPG
Extra junction on roundabout
UndertheWood.JPG (53.16 KiB) Viewed 944 times


As can be seen Under the Wood is not just a track, in fact it's got a small traffic island separating the lanes.

I believe one solution would be to connect Under the Wood to the same node as the A308 Marlow Road. I think that will put the exit count back to 4 which should satisfy most Waze users. Looking at the road geometry I suspect that Under the Wood was originally connected to the same node as the A308 but has recently (quite correctly) been disconnected and that is why it is now mapping differently.

Anyone got any other ideas? Someone has suggested in the UR that maybe marking as a private road would help, does anyone know? I suspect that private roads will still be counted as exits.

Thanks in advance,

Andy.
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Re: Is it Acceptable to Map a Roundabout Incorrectly?

Postby MsDizzie » Wed Jun 25, 2014 7:18 pm

Andy I was thinking "out of the box" re: what would happen if the road was marked up as Private. Its a bit of a puzzle that's for sure.
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Re: Is it Acceptable to Map a Roundabout Incorrectly?

Postby ditchi56 » Wed Jun 25, 2014 7:25 pm

MsDizzie wrote:what would happen if the road was marked up as Private

The private road at this roundabout counts as an exit.
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Re: Is it Acceptable to Map a Roundabout Incorrectly?

Postby ditchi56 » Wed Jun 25, 2014 7:34 pm

AndyPot2 wrote:one solution would be to connect Under the Wood to the same node as the A308

Here's an example of a roundabout with two roads connected to the same node, if you want to play and test the exit counts. I think it has the effect you want.

(Footnote: the exit count effect was not wanted at this example roundabout. The edit was done to stop the constant stream of UR's complaining about Waze routing south to north A24 traffic via the roundabout, instead of staying on the two lanes bypassing it. Despite the incorrect "1st exit" when heading from the south onto the B road, no UR has ever been raised to complain about that.)
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Re: Is it Acceptable to Map a Roundabout Incorrectly?

Postby MsDizzie » Wed Jun 25, 2014 9:15 pm

Thanks for the answers ditchi56 (I'm still learning)
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Re: Is it Acceptable to Map a Roundabout Incorrectly?

Postby ditchi56 » Wed Jun 25, 2014 10:01 pm

MsDizzie wrote:Thanks for the answers ditchi56 (I'm still learning)

Me too!
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Re: Is it Acceptable to Map a Roundabout Incorrectly?

Postby Twister-UK » Thu Jun 26, 2014 12:05 am

AndyPot2 wrote:I believe one solution would be to connect Under the Wood to the same node as the A308 Marlow Road. I think that will put the exit count back to 4 which should satisfy most Waze users. Looking at the road geometry I suspect that Under the Wood was originally connected to the same node as the A308 but has recently (quite correctly) been disconnected and that is why it is now mapping differently.


As the editor responsible for the recent change, here's my reasoning behind it...

In the previous layout, Under the Wood was connected to the southbound one-way segment of the A308, so anyone navigating to UtW would be given slightly dodgy directions to take the nth exit onto the A308 and then turn left, rather than simply taking the nth exit directly into UtW as the real road layout requires. This in itself wouldn't be that big a deal.


More of an issue for me, and the reason I made the change, is that when I'm negotiating a roundabout with directions to leave at the nth exit, I count the actual exits as I drive round rather than counting the nth exit on whatever signage is present leading up to the roundabout and then trying to match what the sign showed with what I see as I proceed around the roundabout. Sometimes the signage presented at each exit doesn't match up with the signage present on the approach, sometimes there isn't any exit signage at all, and sometimes I've simply forgotten what the approach signage said I ought to be seeing on the exit signage :oops:

Counting the actual exits on the other hand generally is pretty foolproof. Granted, there are a few exceptions where you might find an exit stub built in readiness for further roadbuilding that hasn't yet taken place (or never will), or a no-entry road joining the roundabout whos geometry gives the impression that it could also be an exit if you miss seeing the no entry signs or road markings. However, in my experience you're more likely to come a cropper relying on the signage matching up all around the roundabout than you are by counting the visible exits, and in this particular example the UtW exit is sufficiently clear as an exit in its own right that failing to include it in the exit count seems more wrong than leaving it out just to appease whichever muppet at the Highways Agency decided that UtW didn't even deserve the tiniest of stubs on any of the approach signage.

Note also that every alternative mapping source I've checked so far shows UtW as a seperate exit off the roundabout, and as several of those sources are used by other navaids/route planners then it's not just Wazers who get given exit counts that match up with the actual exits but not the approach signage. Not saying that just because everyone else maps it that way that it's the correct way to map it, but given the real world layout of the roundabout I think this is one of those cases where we ought to say stuff the signage, it's what's on the ground that counts.
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Re: Is it Acceptable to Map a Roundabout Incorrectly?

Postby Twister-UK » Thu Jun 26, 2014 6:30 am

ditchi56 wrote:
AndyPot2 wrote:one solution would be to connect Under the Wood to the same node as the A308

Here's an example of a roundabout with two roads connected to the same node, if you want to play and test the exit counts. I think it has the effect you want.


I thought sharing roundabout nodes was still a no-no due to the risk of triggering a 0th exit error?
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Re: Is it Acceptable to Map a Roundabout Incorrectly?

Postby Superfraggle » Thu Jun 26, 2014 8:35 am

It's should be avoided, but there are legitimate cases such as here

https://www.waze.com/editor/?zoom=7&lat ... layers=901

Where you are not allowed to take the first exit, when coming west down the A2, but you can go round the roundabout.
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Re: Is it Acceptable to Map a Roundabout Incorrectly?

Postby Timbones » Thu Jun 26, 2014 9:35 am

Twister-UK wrote:I thought sharing roundabout nodes was still a no-no due to the risk of triggering a 0th exit error?

No it doesn't, it just messes up the node counting.
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