In 1974, the New York City Transit Authority put into service a demo from Germany. It was an articulated built by MAN. It ran on the B88 and the M23.

In 2008, a second demonstrator bus from Germany, this time a Mercedes Citaro O530 Facelift G, was tested for one month.

In this video, we take a look at both German demonstrators that plied the streets of New York City, decades apart.

Note: The follwing information was provided by viewer Glenn Brown, a New York City bus expert, in the comments:
The 1974 M.A.N. articulated is a Model 890 SG. It ran on many express routes (Manhattan, Brooklyn, Queens and Staten Island) on weekdays and on Culture Loop Routes (Manhattan & Brooklyn) on weekends during the Summer of 1974. The Mercedes Citaro Articulated was a test bus for the Orion VII Artic model, because Orion was a major supplier of buses to North America, especially NYC, but Orion did not offer an artic at the time and was losing out on the growing popularity of artics. But as the development program for the Orion Artic was progressing, Mercedes decided to exit the North American Market and sell Chrysler to Fiat and close down Orion (perhaps no buyer could be found). It did continue selling imported Mercedes cars from Germany and it kept Freightliner Truck Division in the U.S.

Thank you, Glenn!