There's a middle ground here.
Get diesel buses, but power them with liquified petroleum gas.
If I understand correctly, only minor modifications have to be done to a diesel engine to enable it to run on LPG.
Most of the school buses here use LPG.
One thing I've noticed is that the engines have something of a "less metallic sound" (i.e., less "rattling") than they would if using diesel. I'm wondering if this results in less maintenance expenses, as well...?
