Natural gas-powered buses rock
 

I drafted behind one for a mile and a half (no stops).

Created a draft so big that I could stay a safe stopping distance behind it and still go 25+ mph.

Is breathing CNG bad for you?

I don't know but it's certainly better than diesel.

It's the particulate matter in diesel exhaust that's really bad to breathe in. CNG burns much cleaner, so the exhaust is probably not as bad. Still, during any kind of physical activity, breathing in a lot of CO2 isn't good for you.

I had to run the ventilation numbers for a propane powered forklift here at work. OMG this beast runs clean! It produces on the order of 1 gram CO per horsepower-hour, where a diesel engine will pump out something like 28 grams per horsepower-hour. Also, very low NOX emissions.

Plus its allways nice to pass through the heat behind the bus on a cold day :) You get atleast one or two seconds of wamth.

CNG buses are AWESOME. I love to follow them on 35 mph speed limit roads where I can comfortably ride behind at up to 40 mph if I get close enough. Riding at a long-term sustainable effort at 40 mph is magical. The blue "CNG" stickers on the back might as well be carrots.

It depends on the bus and the emissions levels. CNG buses without DOCs will emit large quantities of aldehydes, which are really bad for you. Ones with DOCs are probably quite benign.

Newer diesel powered buses will be equipped with particulate filters, and these filters not only trap the smoke, they also tend to burn off the volatile HC and CO emissions.

So basically, just stay away from old buses.

Try to find one running bio-diesel. mmmmm nachos!!