I've been toying with an idea for an evaporative cooling system that would go under the bus. Basically, a 4" sheet-metal tube covered with that synthetic felted fibrous lawn mulch material placed inside a 6" tube, and a drip system to wet the lawn mulch. Fresh air would be drawn in through the 4" tube. Outside air would be blown between the two tubes to evaporate the water from the lawn mulch, thus cooling the walls of the 4" tube. You could fold several lengths of this back and forth under the bus, thus achieving more surface area.
I want to figure this out from a thermodynamic standpoint before putting any money into it, though, and I don't have time to fool with it right now. Or money.