Grodnsk, Poland c. 1908.   Photo from A History of Kosher Bicycles, by Elihu Schemedik, Brandies University Press, 1992.  

Early Budnitz tandem bikes were manufactured with a Rabbi-certified mechitza or “separator wall” (like those used to separate men and women in synagogues), which was mounted between the two seats. 

The company “sponsored” liberal Rabbis who argued that putting a mechitza on a bicycle efficively turned a tandem into two bikes, which made it legal under talmudic law for a husband and wife to ride together.  Orthodox rabbis, paid off by rival bike brands, condemned the design.  The argument continues to this day.