If you've scanned this blog a bit, you'll quickly realize that I'm a wee bit interested in cars.
This post by Our Man In Hanoi, titled "
Four Wheels Bad" piqued my interest. It is also, in part, wrong. Here is the bit:
Well the bikes are the lesser of the evils as far as I can see compared to cars.
While we probably 'agree to disagree' with respect to other parts of the post (industry is the engine of the future and tourism is a nice diversion; a full belly and rubbish on the road is better than hungry cleanliness), and while passenger vehicles may overwhelm the roads, they certainly stress the environment less in comparison to the teeming motos.
How clean are car emissions these days? Well, as one would typically answer a complicated question: "It depends."
Assuming that you chose one of the cleanest (non-hybrid) new passenger vehicle, the emissions output is roughly 1.04 grams* per mile, per this
source from Clean Car Campaign. That asterisk is important - it denotes that I am not well versed on this issue. Emissions is a complicated matter, because what's coming out of the tailpipe is a stream of complicated gases. The four general categories are Hydro Carbons (HC), Carbon Monoxide (CO), Nitrous Oxides (NOx), and Particulate Matters (PM). From my limited research, there seems to be genuine debate on which category is the "worse" for the environment - an important debate to resolve because certain current engine technology can reduce one type of emissions while increasing another. Suffice to say, I don't know enough, so my emissions output metric combines all four categories.
So what exactly is one of the cleanest new passenger vehicle? For the more car-minded folks, it would be a SULEV certified car. Or in other words, something as radical as a
Toyota Camry 4-cylinder sedan, with an automatic.
See EPA numbers here. No need for vehicles with 80 lbs of batteries (which, incidentally, like a
Toyota Prius, would be cleaner still).
So how do motorbikes do? Again, the short answer is: "It depends (but it's worse than the Toyota)."
As this
2000 World Bank study of South Asia (nee India, Bangladesh, Pakistan, Nepal, Bhutan and Sri Lanka) (.pdf file) demonstrates, two stroke engines pollute (~ 20 grams/km) much more than four stroke moto engines (~ 15 grams/km), but both would pollute more than SULEV cars. Note also that if one were to convert to grams/mile, the numbers would be ~ 33 grams/mile and ~24 grams/mile respectively. The study also points out that emissions performance would be severely negatively impacted due to poor quality fuels and lack of engine maintenance.
Even with more advanced engine designs, such as those offered in Europe or the U.S., motorcycles and motorbikes pollute more than cars. Here is the text of the new, more stringent
EPA standards (.pdf file) for motorcyles and motorbikes, issued Dec. 2003. These new standards are more lax than SULEV passenger vehicles, and there are
difficulties experienced by manufacturers in meeting these lower standards.
So in short, how do motorbikes do? 4 strokes are better than 2; 125cc's are better than 50 cc's. The Toyota is much better than all the above.
For those who are shopping, here is a
list, offered by
DriveClean.ca.gov, from which you can pick out cleaner passenger vehicles - note also that PZEV (Partial Zero Emissions Vehicle) is cleaner than SULEVs, and that there are a bunch of PZEV cars out there.