[Talk-us] Complex intersection mapping

Martijn van Exel martijnv at telenav.com
Mon Oct 14 17:42:53 UTC 2013

Hi all,

Here at Telenav we have been looking at complex intersections and we
have set about editing some of these intersections in a way we feel
represents the situation on the ground better than their original
state, and because of that, works better for us. We have received some
feedback on our edits so we wanted to take a step back and see what we
(as the OSM community) think is the preferred way to map these

So what are we talking about? Intersections like this one, where one
or more dual carriageways come together at an at-grade intersection:


One of my colleagues at Telenav has remapped this intersection as follows:


The main difference, and the source of some feedback we have received
over the past few days, is that the dual carriageway roads are
straightened out, creating multiple intersection nodes (4 in this
case) instead of the original single intersection node that connects
all the incoming and outgoing ways. That technique turns out to yield
more reliable and correct routing and guidance ('keep left, turn
right') through these intersections in our testing. But of course,
that cannot dictate how we map as a community, so let's discuss.

Some of the feedback we have received about these edits points to a
statement on this wiki page:
https://wiki.openstreetmap.org/wiki/TIGER_fixup#Braided_streets: 'It
is a reasonable and well-used technique to bring the ways of dual
carriageways back to a single point at intersections to facilitate and
simplify the mapping of control devices and turn restrictions.' In my
mapping across the US, my personal experience has been that this
technique is in fact used, but the 'after' technique with straightened
out ways is actually much more common. I personally prefer that
technique as well - I think it is more pleasing to the eye, represents
what is on the ground better, and is and easier to read. So my feeling
was that this mapping practice would not be disputed. It turns out I
was wrong, so I want to see what the consensus is on mapping
intersections of this type - or perhaps there is none and we can work
together to get there?

Martijn van Exel
OSM data specialist

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