In traffic safety, the so-called safety-in-numbers (SiN) is a well-known effect that is often hard to pin down, and, especially in the not-so-scientific literature, overwrought with too much optimism. Since traffic safety and vision zero is an important building block of an intelligent transportation system, this paper is devoted to describe and analyze this effect with the help of two large databases from Germany. Not too surprisingly, overly optimistic claims like decreasing crash numbers of bicyclists for large bicycle numbers can be dismissed by this analysis, and a much more modest result comes forward: the number of bicycle crashes grows sub-linear with the number of bicycles.