Talk:OSM tags for routing
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maxweight/maxheight
todo here: mention access, and maxweight/maxheight. Morwen 14:35, 9 November 2007 (UTC)
- done with a link to the access-restrictions -page. --MarcusWolschon 15:26, 19 November 2007 (UTC)
Speed
inferring maxspeed
'The default maximum-speed if not given by "maxspeed"=<number> is [dependent on the country and rural / urban classification]' This approach has many disadvantages :
- Testing to see if a point lies in a country Germany is quite difficult. In or outside an urban area is even worse.
- It means multiple routing applications (gosmore, traveling-salesman etc) all contain similar code. Writing, maintaining and testing all these implementations is unproductive.
- The OSM approach has always been not to rely heavily on defaults or implied tags. E.g. religion=christianity does not imply amenity=place_of_worship.
- Mappers are not (supposed to be) lazy. The guides want them to record all kinds of trivial information like source, so they should also be encouraged to add maxspeed tags.
I suggest we move all these recommendations to the relevant country tagging standards pages.
- This would be great but I have some arguments why we still need the defaults
- a) There will always be roads with no maxspeed tag
- b) Regulations change and then there is no way to see if speed is limited by default or by a sign.
- c) Speed-limits ARE very different in other counties. A German Autobahn and a US-highway are 2 separate beasts.
- d) Actually testing if you are inside a polygon is trivial. Just draw a line downward, count the number of intersections and see if they are an odd number. Inner and outher Bounding-boxes speed up this process very well. --MarcusWolschon 12:11, 25 October 2007 (BST)
- Regulations change. So do street names and route numbers. OSM copes by having many energetic mappers.
- Routing software is for people new to an area. They are generally not brave enough to drive at 200km and they tend to fly between major metropolitan areas.
- Furthermore, you will find that the fastest route between 2 points in different cities will rarely change if the average speeds on the motorways changes by 50%. It's like trying to dodge traffic.
- A much easier solution employed by software like Mapsource is to allow the user to specify his preferences. -- Nic 13:57, 25 October 2007 (BST)
- Routing-software not only has to give the fastest route (if that metric is chosen) but also the expected time of arrival. These are speed-limits, thus they form an upper limit to user-entered/automatically determined average-speeds to properly reflect zones where that speed can not be legally reached. If you suggest to ignore speed-related information in the map, then ignore it but don't suggest that others should not include it in the map and find ways to properly evaluate it algorithmically. --MarcusWolschon 05:30, 4 January 2008 (UTC)
- if you don't want to rely on implied tags, you should support efficient data entry. There should not be a need to add maxspeed tags, as long as there's a common rule within the country (e.g. by laws), and to tag exceptions only. Routing should consider those common rules within a country. Otherwise I'd propose a bot that would add maxspeed:implied whereever required. --Traut 15:42, 3 January 2008 (UTC)
- What are you proposing? This page is about how to evaluate the existing and used tags. I consider maxspeed=implied to be a waste of bandwidth because "implied" is simply the default-value for the "maxspeed"-tag. --MarcusWolschon 05:33, 4 January 2008 (UTC)
- The text above claims: Mappers are not (supposed to be) lazy. The guides want them to record all kinds of trivial information like source, so they should also be encouraged to add maxspeed tags.. En contraire. my proposal is NOT to assign maxspeed tags wherever they are the default value within this country. Tagged should be exceptions, but not the defaults. If there would be a need for tags everywhere, those tags should be added by a bot - and they should be marked in a way to differ bot tags from manual tags. --Traut 13:06, 4 January 2008 (UTC)
average speed
B.t.w. why don't we have an averagespeed tag ?
And why doesn't this page mention extraction of average speed data from GPS tracks ? -- Nic 09:47, 25 October 2007 (BST)
- I proposed the average-speed from the osm-gps-tracks myself but it was concluded that this would only work out for the motorways. Because people mapping are driving significantly slower and different from the average user later.
- In fact, I am preparing to collect average speeds for roads in my own navigation-program traveling-salesman but for people who selected "fastest road", "shortest road" and "most fuel-efficient road" and the car-type the user selected "fast", "slow", "bike", "truck",... separately. --MarcusWolschon 12:11, 25 October 2007 (BST)
motorway_link is not always oneway; concept of lanes
Assuming "highway"="motorway_link" to always be oneway is incorrect. At least in Germany there are lots of ways marked by
which are not oneway, but have two lanes of opposite direction (nothing in between other than maybe a painted centerline). In fact, they are something starting from "highway"="service" up to "highway"="secondary", being marked on a part near the Autobahn as belonging to the Autobahn.
- If you ask me, a better concept would have been to map each and every lane on its own and then bundle them to ways
- (since we do now have relations for that purpose, or is it too late already?) --Nodilution 17:48, 26 October 2007 (BST)
- Actually all German motorways I have seen in the map and on the road are 2 oneway-ways (separated by a barrier). That motorway implied oneway is also stated on the German map-features -page. If a single osm-way is used for apart of the road that can be driven in both directions then this is clearly a bug in the map and should be corrected.
- Having a highway as oneway=false in a router would lead to all kinds of problems starting with the router wanting you to turn around or enter the highway on the wrong lane.
- Nic: The parts marked as motorway using that sign would that have no separated lanes (these are required in the law "StVO") would probably better be labeled as trunks with restrictions similar to a "Kraftfahrstraße" as no vehicle <70Km/h is allowed there. --MarcusWolschon 11:11, 31 October 2007 (UTC)
- In the UK there are a couple of single-carriageway sections of motorway still in existence. They have standard motorway restrictions: no stopping, no slow vehicles, 70 mph speed limit, but no physical barrier. E.g. the motorway at Walton Summit, the A601(M) etc. Oneway_yes should not be merely assumed, it *should* be tagged. Richard B 13:06, 31 October 2007 (UTC)
- This is clearly the exception. Thus IMHO "oneway"="no" should be tagged on these few motorways, "oneway"="yes" be assumed and the fact be made known in the documentation for "motorway" and "british tagging-guidelines". --MarcusWolschon 17:49, 19 November 2007 (UTC)
- It's important to make a difference between "motorway"s and "motorway_link"s. Motorways are always oneway (in Germany, too :) ), but in fact, the links to motorways are often divided in to two parts. The first part starts at the road as a bidirectional way, but already has restrictions like a motorway. Then second part follows. The ways gets splitted in a way that comes from the motorway and a way that leads to the motorway. So the two ways of the second part need to be oneway and the first part doesn't.
In short: "highway=motorway" -> "oneway=yes" can be assumed, but "highway=motorway_link" -> "oneway" needs to be set manually and cannot be assumed. --MasterMG 19:23, 20 December 2007 (UTC)- You are probably right. We should not assume oneway=true in general on the links. Can we make a parser to explicitly tag motorway_link-segments that form a Y on a motorway where they have not been tagged in the map? Not change direction or split ways/reverse segments if a oneway=yes or oneway=no is given but add 2 oneway=yes with the correct direction and a oneway=no for the combined part as well as a relation that forbids changing direction at the center-point of the Y. Also add oneway=yes and check the direction of 4-cloverleaf-style intersection (I was more thinking about them then motorway<->trunk -links first.)? --MarcusWolschon 10:56, 23 December 2007 (UTC)
- It's important to make a difference between "motorway"s and "motorway_link"s. Motorways are always oneway (in Germany, too :) ), but in fact, the links to motorways are often divided in to two parts. The first part starts at the road as a bidirectional way, but already has restrictions like a motorway. Then second part follows. The ways gets splitted in a way that comes from the motorway and a way that leads to the motorway. So the two ways of the second part need to be oneway and the first part doesn't.
mph: units
How should speed units be handled e.g. within UK? Should all numbers be given in the common SI units such as km/h for speed or m (meters) for length, width, height? Should numbers be given as used within this country (e.g. mph, feet, stones, ...)? Should non-SI-units be named within the value (such as maxspeed=30mph)? If yes, should those numbers be given with or without space between number and unit? --Traut 15:46, 3 January 2008 (UTC)
- The tags we have clearly state the metric system. You can use let the user choose any unit in the user-interface and convert but the saved map has one unit only at this point and this is good thing. (It started in the UK and still used SI.) --MarcusWolschon 05:21, 4 January 2008 (UTC)
- The article here names within maxspeed/UK: UK mappers will often include units in the maxspeed tag, ie: maxspeed=20mph (miles per hour). What are they supposed to do? Should they name mph? I don't know which UI you refer to - there are different ones, while none of those I used had an option "my numbers will be entered in mph and will be converted to SI units automatically". --Traut 14:29, 4 January 2008 (UTC)
see also
Have a look at proposed features/maxspeed none, please. --Lulu-Ann 16:04, 14 August 2008 (UTC)
