The drivers "cage"... Is that structural?

[FatBoySTL]

My 2003 E350-based short bus has a vertical pole to the right of the driver, with a horizontal pole coming off that around the back side of the drivers seat. It forms a rudamentary "cage" around the driver. Is that structural? Or just a grab bar for folks entering and exiting (that also keeps little Timmy from flying into the driver in hard-breaking situations)?

[cadillackid]

I was told the "stripper poles" found on some busses were designed to help in a rollover situation, but there are plenty of busses without them.. Van cutaways always seem to have them up front

[Danjo]

My Thomas doesn’t have that. Can you post a photo?