Talk:Highway link

From OpenStreetMap Wiki
(Redirected from Talk:Link (highway))
Jump to: navigation, search

Hi All,

I would like to discuss the current implementation of using the highest highway=*_link route possible for link roads.

Using this method there is inconsistent application. Particularly at turning segements which are also marked as link roads but commonly have the lower classification marked. It makes practical sense that it be the lower classification. But that's a big editing task (May be assisted by bulk editing which is easy enough) What's your opinion guys?

Using this method a car magically becomes a part of the highest route even though only one car may travel on that road per day, if it goes into a motorway, its a motorway link. The lower route makes the most practical sense and is what is used by Google, HERE and the state and national government mapping (Which records the official road classifications and heirarchy) of my area (Australia & Western Australia).

Additionally the current justification for higher classification - that link roads have the same attributes or restrictions as the higher classification road is untrue. For Australia wide (I have confirmed this information) it is a typical standard (I can't say for every single situation) that the speed limit remains that of the lower road classification until the slip road terminates. Though speed limit signs may be 150m or so prior to the actual "merge point" there exists no road here in government mapping, that is to say that 150m or so prior to the merge point the slip road is the main road. It is also at this point where you are on the main road that it becomes illegal to have horse drawn vehicles or mopeds or bicycles for example, depending on road. It is not illegal to have these on the link road (again can't confirm every single situation). Another note is that motorway links (controlled access highway slip ramps) can still have driveways or roads leaving and entering it provided there is unimpeded traffic flow whilst a motorway cannot.

As I'm exhausted at the moment XD I'll refrain from going into further detail.

Some clarification examples include:

[1] - [2]

12:00, 3 Feb 2015 (AWST)


Add comment here, include time and date.



so the admonition against tagging for the renderer does not apply here.

Everybody can stop reading after that half sentence. This is a rendering problem, so fix the rendering rules, not the tagging. I thought that this was clearly stated in the original mail discussion. --Cartinus 17:16, 2 July 2010 (UTC)

What's the rendering problem? What's being said there is that whether it's tagged (for instance) primary_link or secondary_link makes no difference to anything except the renderer. --NE2 18:48, 2 July 2010 (UTC)

To render a link properly, it needs to start at one 3-arm node and end at another (3 or more). You get rendering artefacts if it ends at a 2-arm node (unless the two arms happen to be the same colour). The other thing you need to do is to put the link under the two 3-arm nodes at each end. So fine, you might think, just render links under everything (this is what Mapnik currently does). Unfortunately you need to render them on top of any intervening 3-arm node (eg a service road coming out in the middle of a link). The least amount of information you therefore need (to render it neatly) is the lower of the two classifications that the link joins. You render the link just under the lower of the two classifications, and any intervening even-lower classification road goes under the link. If you would prefer the link to be the colour of the higher of the two classifications that the link joins, you also need to know the higher-of-the-two classifications. The higher-of-the-two-classifications is (per the wiki) used as the basis of the highway tag (though this doesn't always happen, because it looks a mess unless it's reasonably symmetrical). Maybe the lower-of-the-two-classifications could be recorded with a links_lower tag. It would be simpler if we recorded the lower classification in the highway tag, and the higher one in a links_higher tag, but maybe life isn't going to be that simple. If you add both links_lower and links_higher tags, then a bot can sort it out one day.--RichardMann 22:30, 2 July 2010 (UTC)

Naming links

How should links be named (to avoid them showing in red in potlatch)?

Don't tag for the editor. If the link has a name, use that. If it doesn't, don't enter a name. (Roughly) all alerts of the data not complying with that/each editor's rules are notices only. Alv 22:23, 22 October 2010 (BST)

Y Junctions should NOT be classified as links.

Observe this Y junction: [3]

2-way roads that split upon arrival of a crossroad should not be classified as links.

My reasoning is as follows

  1. For a highway to be a link, it must branch off another highway that is of the same direction of travel. If a Tertiary Road ends in a Y Junction abutting a Primary Road, you do not have an option to take another route at the split. There must be options in order to classify something as link.
  2. Routing is negatively affected by classifying them as links. A GPS giving turn by turn directions will state "Take the on ramp ahead and follow it onto the Primary Road" Since they are not thought as to be on ramps this can confuse travelers.
  3. Each branch of the Y Junction is still considered the road which it split from. The name of the road should be added to the branches of the Y Junction. Therefore, it is not a _link because _link's do not have names

It seems there is a majority consensus on this based on what I see in OpenStreetMap. However, the picture on the _link page shows Y Junctions being classified as links (???)

If those Y Junctions are links then that would mean, for example in the picture on the official page, the Secondary Road (that turns into a Y Junction) would become a link at the previous node where two Residential Roads intersect the Secondary Road (which makes an elbow turn). BECAUSE at that point, there is no other option other than to merge onto the Trunk Road.

Let me hear your rallying cry and we can settle this!

Wrong. Links are genrally short highways that connect one road with another one, most of them are in fact unidirectional, they have no return from what they come (U-turn is disallowed once you start taking the link).
Also there's nothing in a link that says it is a "ramp". Even if this is the only direction you can take your router will just say "Taking the link and continue on rpad to..." but may still allow before taking it to instruct you to make a u-turn before taking the link.
at end of the link you may still have an option: the target road may be bidirectional or not and you may have to merge or not depending on the number of lanes on the target road, but you won't merge on the link itself, except if the link itself as a reduction of its own lanes (e.g. 2 lanes at start, only one lane before the junction at end of the link).
You're just alone with false reasoning. You are the only one confused.
Your example fits perfectly what are links: the 2 small branches of the Y connecting the north-south street to the west-east road are unidirectional links. The number of unidirectional lanes in the same direction on them does not matter, but what is important is that you must not stop on it except at end, and cannot make a u-turn on it. — Verdy_p (talk) 05:24, 8 December 2017 (UTC)


1. "connecting the through carriageways/through lanes of highways to other roadways of all types" If there are not through lanes which you can branch off from, then it would not be considered a link. This is from the first sentence on the link page. Please thoroughly read the wiki before correcting others. 2. Getting onto a link must always be an 'option' not an obligation. Meaning, if y-junctions are to be classified as links, then you should begin the link classification from the last intersection (wherein exists the last option to turn off and not take the link). Another reason for this is that highways don't randomly turn into links without encountering some sort of junction where you would have an option to go in 2 or more directions. Take this Y-junction as an example [4] Per your faulty reasoning, the residential road would be classified as a link starting at the service road near the clinic. Which brings me to my final point 3. Classifying y-junctions as links yields to an incredibly ugly map. Aesthetics IS important. Y-junctions are minor connectors that do not offer different directions of travel. They are merely a safety feature to avoid driver's from taking up the whole road and thus blocking traffic from incoming cars. It appears you are the only one alone and confused.

U-turns permitted before the tow oneway Y branches means a different topology: in yiour case you have a normal street, finally terminated by two oneway links with no U-turn and no stop (you cannot block the other vehicles. So you're still wrong here. The two branches in your example are really links...

Ok then with the no U-turn you have no prior option to turn off but the service road near the clinic. Thus, per your reasoning, the road would be classified as a link from the service road because a road cannot randomly become a link without a junction that has turning options. This is obnoxious and ugly. Address this issue.

In fact the link includes the full Y up to the intersection to the north, so all 3 branches are links! — Verdy_p (talk) 16:10, 8 December 2017 (UTC)

Ahh, thank you for illustrating the ludicracy of your logic. I believe all can agree with me that having such minor roads be classified as links for that great of an extent is both ridiculous and ugly.

Once again you are using flaming words: this voids all your arguments. You are just starting to contest isolately something that has largely been approved collectively and used without any problem by our millions contributors. Good luck but OSM does not work this way. You cannot contest things alone (and no this is not jsust "my" logic: you are insulting every other people as if they were considering this only as a joke or game, when what they do is serious and they have made many compromizes to adapt to a complex landscape of situations. Apparently you don't seen to understand that cartography has NO rule, only some known best practices, always with exceptions EVERYWHERE you go. — Verdy_p (talk) 18:13, 8 December 2017 (UTC)

Ok, I'm sorry for my 'flaming words'; however, you were the first to be disrespectful. I understand that cartography works this way and that rules and guidelines are under an ever-changing landscape. This issue has not been talked about on this page before and I saw it as being pertinent. The thing about an ever-changing landscape is... that it changes! I saw what I perceive as a broken chain of logic. I want to fix it. During our discussion it is shown that my new rule has plenty of merit. I would like to hear some other users opinions on this however I think we will have to wait a few months for anyone to comment. Once again, it is unfortunate that our discussion took a rude tone, I apologize for my part in it.

No you were the first one to be disrespectful by using the terms "ludicracy of your logic", and even before with "your rallying cry" against the "majority consensus" that you wanted to denounce. You've been flaming since the first post in this thread. — Verdy_p (talk) 20:52, 14 December 2017 (UTC)

The whole point of the talk tab is to parse out things that the majority might do that users see as flaws. Also, 'rallying cry' is not a disrespectful term, I was just trying to add some energy to an otherwise boring topic. furthermore, your logic was ludicrous in my opinion, so I guess I'm sorry if I offended you. Now, as I have previously apologized, can we get back to the issue? Do you not agree that in the stated example changing the dual carriage-way AND the two single carriage ways into links is both ridiculous and ugly? In OSM we need rules that make sense. I stick to my proposal.

I strongly agree with this proposal. All roads have a way to "enter" and "exit" to them. Therefor a Y-Junction should not be classified as links, unless it is a ramp into a Trunk/Motorway. Please consider the thought of an entrance and exit to a road, what is the difference of it being split into a Y-Junction or a normal 2-way connection, if you think Y-Junctions should be links then you should also be making that last section of a way a link regardless of it being a Y or not. This also affects navigation, links do not have names, therefor you would have a "turn right" instead of "turn right into Maple St" for an example. This is common sense, and none of the posts have been disrespectful towards the community. I stand with the Y-Junction NOT as links. -thenodifier