California mulls move to 'zero-emission buses'

Fifteen years ago, California led the way to cleaner transit buses with strict tailpipe emissions standards, which effectively ushered out diesel as the primary fuel for buses in the state and replaced it with natural gas.

Now, California is poised once again to take the lead, this time by mandating a switch to so-called zero-emission buses by 2040.

The new push by the powerful California Air Resources Board has the potential to marginalize natural gas as a bus fuel in the same way its adoption once marginalized diesel.