[aerohead]

I'm going to take a stab at the structure on the tractor,and say that I believe that they are harvesting ram-air pressure from the stagnation footprint to create a 'jet' below the side glass and mirrors,to protect them in a rain from splash and spray,which would create a blind-spot for the driver.
There's already enough leading edge radius for attached flow,and concerning that,the turning vanes would be superfluous.