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    <p>There's a number of initiatives to describe quality of OpenStreetMap, but they're all confined to a specific area. Muki Haklay has done extensive research into data quality of OpenStreetMap. Many quantitative results pertain to the UK. <a href="http://povesham.wordpress.com/" rel="nofollow">His blog</a> is a prime resource if you're looking to learn about the quality of OpenStreetMap in general - which is a lot more than just data completeness. <a href="http://www.josis.org/index.php/josis/article/view/35" rel="nofollow">Here</a>'s his assessment of completeness of OpenStreetMap in the UK. A <a href="http://koenigstuhl.geog.uni-heidelberg.de/publications/2010/Zielstra/AGILE2010_Zielstra_Zipf_final5.pdf" rel="nofollow">comparable study has been done for Germany</a> (PDF) recently.</p> <p>The thing is, to measure completeness, you need an accurate reference dataset to measure against. You could take TeleAtlas or NAVTEQ data for that, but that's expensive data and these companies don't give out their data for research purposes readily. Government data may also be suitable, but is not always available or, as is the case for the US for example, hopelessly outdated and inaccurate. In fact, OpenStreetMap jumpstarted the US mapping effort with a huge import from <a href="http://www.census.gov/geo/www/tiger/" rel="nofollow">TIGER</a>, a dataset which was never intended for routing / navigation and is a topology mess. Volunteers are <a href="http://wiki.openstreetmap.org/wiki/TIGER_fixup" rel="nofollow">working hard</a> to improve that data, but it's slow progress. </p> <p>If you want to give generating quantitative quality metrics a go yourself, your best bet engage with the OpenStreetMap community to learn about the data model and see how it fits with what you're trying to do. What constitutes 'routing data'? The roads and ferry routes themselves, obviously. Turn restrictions? Maximum speeds? Road quality? Grades? The <a href="http://help.openstreetmap.org/" rel="nofollow">OpenStreetMap help forum</a> would probably be a good place to start. My guess is that with a limited budget, you will need to make a lot of assumptions to attain worldwide coverage. </p> <p>HTH</p>
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    1. COThanks for the links - this is more along the lines of what I was I thinking. I had thought about how commercial providers must measure their stats but excluded it from my question which was already a bit long imho (I assume they look at the corrections when they re-survey and then claculate wider stats from this). For OSM measures, you are talking about comparing against inferior data (eg. TIGER/Line) or commercial data (I class OS data as commercial, here!). The latter sort of defeats the my reason for using OSM data.
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    2. COI think topological errors (eg. correct connectedness), attributes (average speeds), and existence are the main potential errors that I am worried about. Errors of a few metres (or even up to 100m) are much less of an issue because I am calculating route distances from city to city. Often with commercial networks I see directional differences of a ~mile due to one way systems, frontage roads,etc.
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    3. COI'm going to award the bounty to this answer - it is the closest to what I was looking for. Although there's work in the area, it looks to be a difficult problem - and a weakness of the OSM approach. Commercial surveyors can compare errors/changes found during re-surveys and estimate an error from this. OSM cannot do this.
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