[Talk-us] Separate relations for each direction of US & State highways.

Tue Nov 19 01:23:01 UTC 2013

Re the comment by  Nathan: “I'm still confused as to why the consumers of a relation can't use the forward/backward roles…” The forward/backward roles only make sense on one-way roads. Other than that, which way is forward and which way is backward? Depends on which way you’re driving down the road. The same thing is true about the left/right thing used in some tags. When I created relations for the WA state routes, I put the cardinal directions in the role for each way. I only used forward in the role when there were separate relations for each direction of the way.

In general, I don’t agree with this proposal unless the highway is divided for its entire length. There are only three state highways in Washington that I can think of where this is true. I know for sure that one of them (WA 512) has a separate relation for each direction, but I don’t know about the other two.

-Compdude

From: Nathan Mills [mailto:nathan at nwacg.net] 
Sent: Monday, November 18, 2013 12:28 PM
To: OpenStreetMap U.S.
Subject: Re: [Talk-us] Separate relations for each direction of US & State highways.

I'm still confused as to why the consumers of a relation can't use the forward/backward roles of the ways referenced therein rather than requiring completely separate relations. Why do we need two or more relations plus a super relation per road route even for undivided highways? Even for a somewhat experienced mapper like myself, it makes the editing process that much more error prone.

-Nathan

Chris Lawrence <lordsutch at gmail.com> wrote:

On Mon, Nov 18, 2013 at 10:52 AM, Paul Johnson <baloo at ursamundi.org> wrote:

Not a fan.  It greatly complicates things for information that can either be gleaned obviously or is a "nice to have."  Having 3+ relations for something that isn't fully divided just complicates things, with the exception edge case of a relation that starts or ends on a divided highway.

On Sun, Nov 17, 2013 at 9:30 AM, James Mast <rickmastfan67 at hotmail.com> wrote:

I'm just curious, but what's everybody's opinion on this?  I know it's acceptable for the Interstates (some are setup this way, some aren't) since they are all divided, but what about for US Highways and State Highways?  I know that we want to eventually have the cardinal directions in OSM for the routers so they can properly tell people which direction the of the highway they need to turn onto (like turn left onto Westbound US-30).
....
Also, on a side note, do you guys think we should remove the "symbol" tags in the relations from all the Interstates/US highways they show up in at the same time?

So, let's get this discussion going!

IMO direction-based relations, with correct forward/backward tagging, are borderline necessary for directions based on relations to work correctly in the US and Canada. That's something that's sorely lacking (along with exit numbers and usage of "destination" tags) in OSRM today.

All we should need is a single super relation for each route, along with reasonable numbers of directional relations with way members - since each directional relation will have 1/2ish the number of members, there's no reason to confine them to one per state unless we're doing that to match up with Wikipedia articles.

As for symbol tags, I'd vote to transition them to the wiki:symbol namespace if possible.

Chris

-- 
Chris Lawrence <lordsutch at gmail.com>

Website: http://www.cnlawrence.com/ 

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