## 3 OSM Street Network Evolution  
### User Activity and Data Development  
The number of OSM participants in Germany increases from year to year. To date (June 2011), a total of more than 40,000 different members have actively contributed to the project. Slightly different numbers of contributors have generated the three OSM object types: Nodes, Ways and Relations (Figure 1). Another interesting fact, also presented in Figure 1, is shown by the lines in orange, light blue, and purple, representing the users that generated a total of 98% of the data volume of each respective object type. Here 98% of about 74 million Nodes can be attributed to approximately 8,500 members, 98% of about 11 million Ways to approximately 7500, and 98% of about 171,000 Relations to approximately 2,600. These numbers are based on the information in the database on who has been saved as the last owner of each Node, Way, or Relation. To be able to give more information about the results conducted during our analysis, we need to introduce the three object types that are used in the OSM project/database in greater detail. A Node is the basic object in the database and constitutes a coordinate. Ways represent lines or surface objects and constitute references to Nodes. Objects can be linked via Relations, which relate to each other. The results of our analysis showed a general pattern of an increase in the number of OSM Node and Way objects over the past few years (2007-2011) (Figure 2a,b), which was expected due to the general trend that OSM showed in Germany in recent years. Figure 1: Number of OSM Contributors in Germany from 2009 to 2011. However, due to the three-month interval used in this analysis, other factors can be interpreted and distinguished. The data clearly shows that during the summer months the members are more active than during the winter months. Also, an above-average increase in data can be noticed at the turn of the year 2010/2011 and in spring 2011. The high proportion of new objects during these points in time can be attributed to the release of the Bing aerial images for digitalization purposes. The negative trend for Ways in OSM at the beginning of 2007 is due to the API changes during that year. With these changes the data schema and representation has been adjusted, and the total number of Ways was affected in this way; however, no data was lost by this change. In prior studies the development of the German street network has only been compared to a commercial dataset (TomTom) for a period of eight months [32]. Neither definite statements about when different street types can be considered relatively complete nor a projection for the future were given. In our analysis the strongest increase in transportation-related routes in OSM for Germany to date could be distinguished in the third quarter of 2008 (+180,000 km) (cf. Figure 3a,b). The year 2008 was also when the most transport routes were added to the OSM database in general with a total length of almost 530,000 km. Since 2008 the annual expansion has decreased over time, and a slight change is discernible for the first half of 2011, where the trend slightly increases again. However, if this  
Figure 2: (**a**) Development of OSM Nodes in Germany; (**b**) Development of OSM Ways in Germany. tendency continues for the rest of 2011, a small increase in the total street network will be detected for this specific year. After gaining this first general impression about the development of the German OSM dataset, we conducted further analyses to give more detailed information about the street network. Due to the fact that every country's street network consists of several different street categories, it seemed mandatory to consider these in our analysis.