<div dir="ltr"><div class="gmail_quote"><div lang="EN-US" link="blue" vlink="purple"><div><div>Hello All,<br><p><u></u></p><p><u></u> <u></u></p><p>My name is Kristen and I am the colleague that Martijn mentioned in his e-mail regarding complex intersection mapping. I am also the recipient of the messages of disagreement from Minh. I am chiming in because my edit is an example cited by Martijn and that I have received feedback regarding my edits of intersections. <u></u><u></u></p>
<p><u></u> <u></u></p><p>During my time editing OSM data I've encountered instances of intersections that include, but not limited to: <u></u><u></u></p><p><u></u> <u></u></p><p>• Dual carriageway road intersecting with a road that changes from a dual- to single carriageway roadway at the intersection (example 1)<u></u><u></u></p>
<p>• Single carriageway road intersecting with a road that changes from a dual- to single carriageway roadway at the intersection (example 2)<u></u><u></u></p><p>• Dual carriageway road changing to a single carriageway road intersecting with another dual carriageway road changing to a single carriageway road (example 3)<u></u><u></u></p>
<p>• T-intersection with an island facilitating and protecting vehicular movement (example 4)<u></u><u></u></p><p><u></u> <u></u></p><p>Images of the types of cases I’ve encountered and tackled can be found here: <u></u><u></u></p>
<p><u></u> <u></u></p><p><a href="https://www.evernote.com/shard/s366/sh/914b7699-8377-4862-b90b-e56f5d41792d/d42f6f273b15e84d1ba309d3b4be998b" target="_blank">https://www.evernote.com/shard/s366/sh/914b7699-8377-4862-b90b-e56f5d41792d/d42f6f273b15e84d1ba309d3b4be998b</a><u></u><u></u></p>
<p><u></u> <u></u></p><p>The goal of my edits was to best model the vehicular movement through an intersection---especially those that involved changing road configuration. I forked the single-carriageway to a dual carriageway prior to the actual intersection so it’d be consistent with the dual carriageway road configuration within the intersection. I acknowledge I could have forked the single carriageway within the intersection box, or forked together the two directions of a dual carriageway to a single carriageway through the intersection (Martin’s example, attached). However, neither technique “looked right” in terms consistency to how things looked on the ground (aerial). This obviously is debatable. Feedback on my examples *with* illustrations—like Minh’s response-- would be super helpful in facilitating this discussion and work toward a consensus.<u></u><u></u></p>
<p><u></u> <u></u></p><p>As I said early there are a few folks that actually contacted me about my edits. One has joined the discussion, another is following it, the third I’m not sure. If you’re out there, please don’t be shy, chime in!<u></u><u></u></p>
<p><u></u> <u></u></p><p>That’s my $0.02<u></u><u></u></p><p><u></u> <u></u></p><p>Best,<u></u><u></u></p><p><u></u> <u></u></p><p>Kristen<u></u><u></u></p><p><u></u> <u></u></p><p>---<u></u><u></u></p><p><u></u> <u></u></p>
<p>OSM Profile → <a href="http://www.openstreetmap.org/user/KristenK" target="_blank">http://www.openstreetmap.org/user/KristenK</a><u></u><u></u></p><p><u></u> <u></u></p><p><u></u> <u></u></p><p>-----Original Message-----<br>
From: Minh Nguyen [<a href="mailto:minh@nguyen.cincinnati.oh.us" target="_blank">mailto:minh@nguyen.cincinnati.oh.us</a>] <br>Sent: Tuesday, October 15, 2013 2:52 AM<br>To: <a href="mailto:talk-us@openstreetmap.org" target="_blank">talk-us@openstreetmap.org</a><br>
Subject: Re: [Talk-us] Complex intersection mapping<u></u><u></u></p><p><u></u> <u></u></p><p>On 2013-10-14 10:42 AM, Martijn van Exel wrote:<u></u><u></u></p><p>> So what are we talking about? Intersections like this one, where one <u></u><u></u></p>
<p>> or more dual carriageways come together at an at-grade intersection:<u></u><u></u></p><p>><u></u> <u></u></p><p>> <a href="https://www.evernote.com/shard/s9/sh/6438c196-bb92-4f66-81dc-9b7518628" target="_blank"><span style="color:windowtext;text-decoration:none">https://www.evernote.com/shard/s9/sh/6438c196-bb92-4f66-81dc-9b7518628</span></a><u></u><u></u></p>
<p>> 6ba/0e8f07ff527c6a85c0dec426b9b79f1e<u></u><u></u></p><p>><u></u> <u></u></p><p>> One of my colleagues at Telenav has remapped this intersection as follows:<u></u><u></u></p><p>><u></u> <u></u></p><p>> <a href="https://www.evernote.com/shard/s9/sh/3491f1fe-6afa-4571-bc43-7cb31c9c2" target="_blank"><span style="color:windowtext;text-decoration:none">https://www.evernote.com/shard/s9/sh/3491f1fe-6afa-4571-bc43-7cb31c9c2</span></a><u></u><u></u></p>
<p>> 625/9dd47d1445fdcf03d3f0bbd93b8e0f92<u></u><u></u></p><p>><u></u> <u></u></p><p>> The main difference, and the source of some feedback we have received <u></u><u></u></p><p>> over the past few days, is that the dual carriageway roads are <u></u><u></u></p>
<p>> straightened out, creating multiple intersection nodes (4 in this<u></u><u></u></p><p>> case) instead of the original single intersection node that connects <u></u><u></u></p><p>> all the incoming and outgoing ways. That technique turns out to yield <u></u><u></u></p>
<p>> more reliable and correct routing and guidance ('keep left, turn<u></u><u></u></p><p>> right') through these intersections in our testing. But of course, <u></u><u></u></p><p>> that cannot dictate how we map as a community, so let's discuss.<u></u><u></u></p>
<p><u></u> <u></u></p><p>I'm one of the troublemakers who complained about your colleague's edits. However, the example you give bears little resemblance to the intersections I disagree on. Your "before" screenshot depicts individual lanes (ew) that converge into a single-point intersection, even when the main road is divided on both sides of the intersection (ew). My quibble relates to divided roads that become undivided at an intersection.<u></u><u></u></p>
<p><u></u> <u></u></p><p>Screenshots tell it best, but unfortunately we don't seem to have a tool to visualize historical revisions of ways. So I recreated their changes from memory in iD (because that's how I roll).<u></u><u></u></p>
<p><u></u> <u></u></p><p><u></u> <u></u></p><p><u></u> <u></u></p><p>** Example A **<u></u><u></u></p><p><u></u> <u></u></p><p>Ryans Way and Sycamore Grove Ln. meet Fields Ertel Rd. at the same intersection. Fields Ertel is undivided. Ryans Way is briefly divided at the subdivision entrance, a very common configuration in newer subdivisions, but Sycamore Grove is not.<u></u><u></u></p>
<p><u></u> <u></u></p><p>I mapped the intersection as a single point:<u></u><u></u></p><p><u></u> <u></u></p><p><<a href="http://nguyen.cincinnati.oh.us/minh/osm/talk-us/braided_intersections/ryans_before.png" target="_blank"><span style="color:windowtext;text-decoration:none">http://nguyen.cincinnati.oh.us/minh/osm/talk-us/braided_intersections/ryans_before.png</span></a>><u></u><u></u></p>
<p><u></u> <u></u></p><p>Your colleague redrew it as a two-point intersection, dividing the very tip of Sycamore Grove (to the south):<u></u><u></u></p><p><u></u> <u></u></p><p><<a href="http://nguyen.cincinnati.oh.us/minh/osm/talk-us/braided_intersections/ryans_after.png" target="_blank"><span style="color:windowtext;text-decoration:none">http://nguyen.cincinnati.oh.us/minh/osm/talk-us/braided_intersections/ryans_after.png</span></a>><u></u><u></u></p>
<p><u></u> <u></u></p><p>I prefer the former approach, because the latter shows a false traffic island on the south side of the intersection. Imagine a pedantic navigation tool that tells a driver coming from Sycamore Grove to "keep/bear right and immediately turn left".<u></u><u></u></p>
<p><u></u> <u></u></p><p>** Example B **<u></u><u></u></p><p><u></u> <u></u></p><p>A divided Main St. intersects a divided Remick Blvd. Like everyone else here -- and unlike the "before" example Martijn provided -- I prefer a four-point intersection. But just to the east, Remick and a service road both become undivided at the same intersection. I mapped it as a single<u></u><u></u></p>
<p>point:<u></u><u></u></p><p><u></u> <u></u></p><p><<a href="http://nguyen.cincinnati.oh.us/minh/osm/talk-us/braided_intersections/remick_before.png" target="_blank"><span style="color:windowtext;text-decoration:none">http://nguyen.cincinnati.oh.us/minh/osm/talk-us/braided_intersections/remick_before.png</span></a>><u></u><u></u></p>
<p><u></u> <u></u></p><p>Your colleague redrew it as a four-point intersection, this time with two triangles:<u></u><u></u></p><p><u></u> <u></u></p><p><<a href="http://nguyen.cincinnati.oh.us/minh/osm/talk-us/braided_intersections/remick_after.png" target="_blank"><span style="color:windowtext;text-decoration:none">http://nguyen.cincinnati.oh.us/minh/osm/talk-us/braided_intersections/remick_after.png</span></a>><u></u><u></u></p>
<p><u></u> <u></u></p><p>** Example C **<u></u><u></u></p><p><u></u> <u></u></p><p>Originally, State Route 4 became undivided at an intersection with Walden Ponds Cir. (divided) and Fairham Rd. (undivided). SR 4, with a speed limit of at least 45 mph, was redrawn to shuffle about 25 feet to the left right after the intersection. But on major roads like SR 4, the landscaped median ends several hundred feet before the intersection to make room for a long left-turn lane. So I prefer to join the carriageways atop the left-turn lane, at a much gentler angle, without cutting into the median.<u></u><u></u></p>
<p><u></u> <u></u></p><p>Since I first mapped the area, the median on SR 4 was extended well past this intersection, so no "braiding" was necessary:<u></u><u></u></p><p><u></u> <u></u></p><p><<a href="http://osm.org/browse/way/240893333" target="_blank"><span style="color:windowtext;text-decoration:none">http://osm.org/browse/way/240893333</span></a>><u></u><u></u></p>
<p><u></u> <u></u></p><p><u></u> <u></u></p><p><u></u> <u></u></p><p>In all three examples, my original rendition was called "braiding", but the ways were never intertwined as in the much-ridiculed TIGER data.<u></u><u></u></p>
<p><u></u> <u></u></p><p>I don't know what specific issues you found with the way I'd been mapping. But I think routers should handle both styles gracefully, because mappers will intuitively gravitate towards one or the other, depending on what factors they consider. As intersections go, these examples are rather straightforward. On the other hand, I've mapped plenty of intersections where the traffic engineers clearly got carried away. If someone corrects me on one of those, I'm all ears! :-)<u></u><u></u></p>
<p><u></u> <u></u></p><p><<a href="http://osm.org/browse/relation/1843583" target="_blank"><span style="color:windowtext;text-decoration:none">http://osm.org/browse/relation/1843583</span></a>><u></u><u></u></p><p>
<<a href="http://osm.org/browse/relation/1284976" target="_blank"><span style="color:windowtext;text-decoration:none">http://osm.org/browse/relation/1284976</span></a>><u></u><u></u></p>
</div></div><p><<a href="http://osm.org/go/ZR~9kObUM" target="_blank"><span style="color:windowtext;text-decoration:none">http://osm.org/go/ZR~9kObUM</span></a>><u></u><u></u></p><div><p><u></u> <u></u></p>
<p>--<u></u><u></u></p><p><a href="mailto:minh@nguyen.cincinnati.oh.us" target="_blank"><span style="color:windowtext;text-decoration:none">minh@nguyen.cincinnati.oh.us</span></a><u></u><u></u></p><p><u></u> <u></u></p><p>
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