The OSM street network is more than 80% complete

Posted by amb_santacruz on 13 August 2017 in English (English)

Chris Barrington-Leigh and I have been working for the past few years to assess the completeness of the street network in OSM. We're pleased to have now published our results in the journal PLoS ONE. Thanks to many suggestions from the OSM community on our preliminary analysis.

Here are the highlights from the paper's abstract:

We find (i) that globally, OSM is ∼83% complete [as of January 2016], and more than 40% of countries—including several in the developing world—have a fully mapped street network; (ii) that well-governed countries with good Internet access tend to be more complete, and that completeness has a U-shaped relationship with population density—both sparsely populated areas and dense cities are the best mapped; and (iii) that existing global datasets used by the World Bank undercount roads by more than 30%.

An update using the April 2017 snapshot suggests that completeness is now ~89%. Our more detailed results and all our code are available on GitHub. Here's a sample of the largest 10 countries (updated through 2017), showing the actual growth in OSM road length and our model fits: Growth in OSM dataset

And here's the fraction complete, also updated through April 2017: Fraction complete map

Location: University of California Santa Cruz, Santa Cruz, Santa Cruz County, California, United States of America

Comment from MapMakinMeyers on 14 August 2017 at 00:59

I map a lot of places in OSM. ( I think your numbers are way off (especially after looking at your first post, now your new number). Do either of you actively map in OSM? You would get a better feel for what is missing where and have a better grasp on completeness.


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Comment from amb_santacruz on 14 August 2017 at 15:28

Thanks for the thoughts. I have done a little mapping in OSM, mainly with my students in class projects, but our conclusions are based on the visual assessment and modeling described in the paper. I'm curious why you think the numbers are way off? Note that large countries such as the US (which alone accounts for nearly a quarter of the world's roads) push the global average up, even if many other countries are much less complete than the global average of 83%.

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Comment from rab on 14 August 2017 at 16:31

Your figures may be right, where a strong local community is present. But in Africa, where most of the content was added during missing map campaigns we have large areas with absolut unusable data.

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Comment from imagico on 14 August 2017 at 17:02

So in 2015 you estimate road mapping in OSM to be 90% complete. Now you have improved your methodology and have a revised estimation that it is 83% complete.

I would predict that in 1-2 years we will get yet another improvement in methods and you then predict about 75% completeness. ;-)

Seriously: The value of such research should not be measured in terms of the sophistication of the methods used but based on the actual predictive power of the estimations made. Most of the "90% and more" estimations for individual countries i would regard pretty useless (for countries like Niger this is quite clearly wrong). But the information which countries still miss a large portion of the road network is potentially quite useful.

To be fair it should also be pointed out that the level of completeness can actually decrease in reality as new roads are built/established. This can be quite significant as an influence especially in developing countries.

I could not find any definition what you consider a road. The distinction between roads and highway=track in OSM is for example often not so simple. Tagging something that is actually highway=service or highway=unclassified with surface=unpaved as highway=track is quite common in OSM.

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Comment from MapMakinMeyers on 14 August 2017 at 17:52

where do you get the ~23% of the world's roads are in the US figure from? I didn't see a source for that figure in the paper?

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Comment from amb_santacruz on 14 August 2017 at 22:27

Thanks for the additional comments. Some clarifications:

  • We consider the following highway tags to be roads: motorway, motorway_link, trunk, trunk_link, primary, primary_link, secondary, secondary_link, tertiary, residential, road, unclassified, living_street. We don't consider highway=service or highway=track, as these generally represent access to fields, parking lots, driveways, etc. See p.6 of the paper. Note that even in countries like Germany where the road network was complete in OSM many years ago, these "other" highways are still growing rapidly (see the figure above, which shows trends for "other paths").

  • The figure that ~23% of the world's roads are in the US comes from our analysis, and thus depends on our estimated level of completeness. But it's comparable to other sources. For example, IRF World Road Statistics suggests that 18.4% of the world's roads are in the US. This 18-23% range seems reasonable when one considers the low density of most US urban development (meaning that each km of residential road in the US serves many fewer people), and the extensive network of rural roads.

It's an important point that the length of the road network is a moving target, as new roads are built. We don't attempt to capture this dynamic. However, I'd be very surprised if physical roads were increasing faster than additions to the OSM database.

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