Strange object on Man Lions City Bus in World Transit Systems Posted March 1, 2013 · Edited March 1, 2013 by Bustitution Not sure if this was the right place to post this. The MAN Lion's City buses are my favorite. But as I was looking at pictures I noticed every bus has a flat cylindrical object sitting on top of the bus at the rear. I noticed that on the 12m buses there are only 2 but the 18m buses have 4, 2 on each section. I recently found a picture of a 12m CNG bus that has 3 of these objects on the roof In this picture you can see the objects on the roof over the rear sign and you can see it again in this picture, the 2 objects are next to the last rooftop emergency hatch You can also see it on all of the buses in this picture as well I know the MAN Lion'S City buses are most common in Europe and Spain. Does anyone what what these objects or devices are? I'm trying to shine some light on this since I have no clue what these objects are. I hoping anyone would know more about these buses than me.