California Air Resources Board

In back-to-back rulings, the Californian Air Resources Board approved the nation's strongest climate protection plan and the strictest on-road diesel emissions plans that will mean the oldest, most polluting trucks and buses will soon be no more.

At a crucial two-day meeting, the California Air Resources Board may adopt, reject or modify two separate, landmark, controversial plans - one on climate change, the other on diesel emissions from trucks and buses.

In the San Francisco Bay Area, two public transit agencies are conducting trials with "Zero Emission Buses", or ZEBs. They are using different types of hydrogen fuel cell technologies, with very different results.