## 3 OSM Street Network Evolution
### Data Completeness and Population Density  
For further, more detailed studies of the route length of the total street network, the dataset was divided into the smallest possible German administrative units: municipalities and town boundaries. Detailed presumptions about the data development and the relative completeness with regard to population and area can be provided as a consequence of calculating the length of the route network for the different modes of transportation within the specified boundaries. The administrative areas used in our analysis (12,387 in total) feature the number of inhabitants for the years 2008 and 2009 and were obtained from the TomTom Multinet dataset. The entire administrative area dataset is subdivided into six groups considering different population numbers. The first group (\(\geq\)1,000,000) represents metropolitan areas; the second group (\(\geq\)500,000 and \(<\)1,000,000) large towns; the third (\(\geq\)100,000 and \(<\)500,000) towns; the fourth (\(\geq\)50,000 and \(<\)100,000) medium-sized towns; the fifth (\(\geq\)10,000 and \(<\)50,000) small towns; and the last (\(<\)10,000) rural towns. With regard to the entire administrative area of Germany, this means that approximately 73% of the entire population lives in population groups one to five, covering one third of the entire area of Germany. Conversely, around 27% of the population lives in population group six (rural towns) and is distributed over two-thirds of the total area of Germany. For our analysis we considered the development of three different street networks: total street network, and car and pedestrian networks (Figure 7a). The rows in Figure 7a visualize the expansion for each individual network and percentage of new data per year. It is evident that over the past four years, the route network of the individual groups has developed in correlation to their population density. While the general route network has been less active in the more densely populated areas, an increase in new data can still be seen in the more sparsely populated areas. It is also clearly discernible that the largest overall increase in new streets occurred in 2008. Figure 7: **(a)** Development of OSM Street Network by Town Type; **(b)** Relative Difference by Town Type and Street Network (June 2011). Another aspect that has been included in our analysis was the difference in total length of the route networks by town or municipality (Figure 7b). The results showed that the aforementioned approximately 9% of missing data is mainly distributed over the sparsely populated areas. It is also clearly discernible that OSM provides more overall data in comparison to the proprietary dataset with regard to the total and pedestrian route network length. When expressed in route network lengths, this means that in mid-2011, OSM was still lacking approximately 3% (21,000 km) in the small-town population group and approximately 6% (48,000 km) in the rural-town population group. Using these highly detailed studies for the increase in street data for the different town types and the analyses of the differences in route network lengths in comparison with a commercial dataset, projections could be made of the time frame within which the dataset could be completed (at least in a relative comparison to another dataset, since neither of the datasets represent ground truth). As Figure 7b indicates, there is currently still a lack of data for less densely populated areas in OSM. Figure 7a shows the development of data by population group. In line with the expansion rate of this graph, 6% (14,000 km) of new streets were added to group 5 for car navigation in 2010 and nearly 10% (33,000 km) to group 6. By mid-2011, 2% (5,000 km) of new streets were added to group 5 and slightly less than 4% (16,000 km) to group 6.