The term "rigid bus" is not used in American English, where the distinction is commonly made using the term "non-articulated" bus or, when the context is clear, "standard bus". However, the term "standard bus" can be confusing, because it is sometimes used, in other English-speaking countries, referring to a uniform bus design developed for and by a number of European bus manufacturers, in two model generations, between the 1960s and the end of the 20th century. The German VöV-Standard-Bus includes the Mercedes-Benz O305 and the Mercedes-Benz O405 types, each of which, in both rigid and articulated forms, was widely acquired and used by bus operators in English-speaking countries outside North America.[2]