  Urban road networks have distinct geometric properties that are partially
determined by their (quasi-) two-dimensional structure. In this work, we study
these properties for 20 of the largest German cities. We find that the
small-scale geometry of all examined road networks is extremely similar. The
object-size distributions of road segments and the resulting cellular
structures are characterised by heavy tails. As a specific feature, a large
degree of rectangularity is observed in all networks, with link angle
distributions approximately described by stretched exponential functions. We
present a rigorous statistical analysis of the main geometric characteristics
and discuss their mutual interrelationships. Our results demonstrate the
fundamental importance of cost-efficiency constraints for in time evolution of
urban road networks.
