On the outside, they are the same big yellow school buses, but their fuel is different. More than 170 buses in Pinellas, Hillsborough, Pasco and Polk counties run on propane.

The Bluebird Bus company says these vehicles emit 80 percent less smog. In Polk County, there are 10 of these new buses and five more are coming.

“The advantages we have found on the propane buses are decreased fuel costs, and also the stability of fuel cost over diesel and gasoline fuel costs," says Scott Reeves, support services of Polk County Schools.

And they are quieter says the district, which said it pays $1.86 per gallon for diesel fuel, but only $1.13 for propane.

For more information click here