[OSM-talk] Roundabouts - why is a separate segment required?

Darafei "Komяpa" Praliaskouski me at komzpa.net
Thu Feb 15 08:53:47 UTC 2018


>
>
> To repeat myself. You can determine if you need to "drive on this round
> way" from a single node. No need for a section between entrance & exit.
>

You can. You're at it now.
Someone else can be thinking of all the other cases while implementing
their thing.

Sometimes people think "this is obvious, everyone will parse it that way",
and then find out that someone just checks oneway tag for non-empty and
their oneway=-1 are shown in reverse, and there's nothing you can do about
it.

You can either make an ambiguous scheme that allows two different
interpretations ("you enter roundabout the moment you touch the way" and
"you did not enter roundabout and it's just a turn") and have difficulties
counting exits. Or you can follow the suggestion, add a small segment and
make the data that can be understood in the same way by consumers with
different assumptions.

It's better to have compatible defaults.
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