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Forgive me for asking so many questions these couple days, but I'm confused on road classification. For example, the road that is currently set to "secondary" now here is the main street of the city (Thomasville). It has most of the city's restaurants and shops, it's a state highway, and it has it's own interstate exit. Highway 109 links Winston-Salem (Population: 236,000) to Thomasville (Population: 26,000) and it continues through Uwharrie National Forest. I wouldn't say it links "large cities" (It links a large city and a small city IMO), but it does get a lot of traffic. It has five lanes counting the center turn lane, and is considered a "major artery".

asked 20 Apr '15, 20:40

AmaryllisGardener's gravatar image

accept rate: 0%

I would ask this question on the talk-us mailing list.

(20 Apr '15, 21:12) RM87

There has never been a totally unambiguous definition of road classifications in the US. In most places, US highways are given the primary designation, and state highways are given the secondary designation, except where they clearly meet motorway or trunk classification. So this highway meets part of the Primary definition, and part of the Secondary definition.

The OSM usage of primary and secondary roads also may not match common usage by other organizations such as the state highway department.

[edit]In the end, routers only use road classification if there are no additional road attributes. The more important attributes for router hints are traffic signals, road width, lane count, speed limit, and turn lane tagging.

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answered 21 Apr '15, 12:38

Mike%20N's gravatar image

Mike N
accept rate: 17%

edited 21 Apr '15, 17:44


Road classification has some impact on the default speed limits, see e.g. this Graphhopper file where primary roads have a maxpspeed of 65 km/h , secondary 60, tertiary 50 km/h. I assume this is for Europe

(21 Apr '15, 13:00) escada

OSRM has a similar profile file. Stating that routers often do not take road classification into account is misleading. They have to if no or only few other properties are present.

(21 Apr '15, 14:14) scai ♦

I tried looking at the file with speeds in I think they might be a bit too slow for km/h they may actually be a fallback for german users in mph as the UK motorway national{ie default} speedlimit 112kph/70mph and Germany has a recomended default of 130kph/80.78mph 100mph speading isn't uncommon in europe and its been common at times in near pass for most cars on the motorways to be going between 80-90mph.

(21 Apr '15, 15:14) Govanus

The authorities decided not to raise the limit to avoid encorageing even faster excesses but did regularly take a dim view at at someone trying to go over 90mph without a good reason and striped the licence from those over 100mph mainly on compartive passing safety grounds when lorrys are limited to far lower speeds

(21 Apr '15, 15:17) Govanus is a good guide thoughI'm not sure if the recent move to add 10mph increases to meny lorry speeds to improve speed differance to cars held up and passing unsafely has been reflected yet

(21 Apr '15, 15:18) Govanus

@Govanus Routers are usually not interested in maximum speed but in average speed instead. But this issue is not relevant to the original question.

(21 Apr '15, 15:52) scai ♦

I just wanted to give you guys a heads up that after reading "Highway:International equivalence" on the wiki, I'm going to go ahead and change Randolph Street from secondary to primary.

(23 Apr '15, 15:57) AmaryllisGar...

Mike N - good answer, but bear in mind that there are many routers for many different types of transport. Your logic holds true for a car router, but as someone who runs a bike router, I'm interested in the roads that are less likely to be full of fast car traffic. highway= classification is a good shorthand for that.

(23 Apr '15, 22:57) Richard ♦
showing 5 of 8 show 3 more comments

Hi AmaryllisG?

Well I'm not too sure but the basic history of changesets suggests that you may have deleted the orignal road during your edits if you can find the changeset for your deletion then look at the bit you may have deleted history it will give an author that made the original choice. I bagan that with the newer version but it seems that it may just point back to you if you edit under the similar name of AmaryllisG if by coincidance I'm wrong then I appoligise and try using either:-

or better the discussion box on the side panal of:-

asking direct can give you a good answer and a rapid change of hart if they where working from skeetchy sources.


That apart all I can point you two is the main guidance at:-

and these country specific pages:- and this one that seems very comprehanive for the USA and offers a few clues maybe in the demotion reasons under secondary tag around 3/4 of the way down the page:- []{}

I thought before looking properly that it might not have gone very far but the NC109 dose seem to get around to several places and shadows an motorwy/intate road at a distance. I guess that unless it was mapped in patchs with differeng views someone might be classing it on volume of traffic as being lighter there (the exit might not be popular in someone elses ideas). try looking at the historys of the other parts of the NC109 on OSM and ask them there reasoning. suggests someone may have made an uncorrected mistake 5 years ago when they things primary? try asking them here:-

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answered 20 Apr '15, 21:35

Govanus's gravatar image

accept rate: 3%

AmaryllisG is the name I use when editing OSM. I can't see that I ever changed Randolph Street to "secondary".

(20 Apr '15, 21:59) AmaryllisGar...

It also has the tag tiger:reviewed=no, which means that the classification probably comes from the Tiger import and was never reviewed. AFAIK this tag is removed when a mapper has validated all the tags and updated them to reflect the reality.

(21 Apr '15, 08:02) escada

Looking at the history of the original Tiger ways there has been some review; just no-one's removed that tag:

Your way was split from one of those I think (you can get an idea of what happened by looking at the history of your way, looking at the changeset in which the v1 version was created, and looking at other adjacent ways in there to see what it was split from).

(21 Apr '15, 09:35) SomeoneElse ♦

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question asked: 20 Apr '15, 20:40

question was seen: 7,719 times

last updated: 23 Apr '15, 22:57

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum