A recent column in the Los Angeles Times painted a grim picture for motorcyclists based on emissions data. The story, "Inconvenient Truths About Motorcycles and Smog," explained how motorcycles emit more nitrogen oxides-NOX, byproducts of combustion that contribute to smog-and concludes by claiming that "Motorcycles, even small ones, are more polluting than Hummers."
Saying that a motorcycle pollutes more than an SUV because it emits more nitrogen oxides is like saying soda is more healthy for you than juice because soda has fewer calories. There is a lot more involved in vehicle emissions than just nitrogen oxides, and the column in the Times is, at best, misleading. It claims that "the average motorbike is about 10 times more polluting per mile than a passenger car, light truck or SUV, according to a California Air Resources Board comparison of emissions-compliant vehicles." I couldn't find the referenced CARB document on the agency's website, but I did find actual emissions test data for cars, SUVs and motorcycles on the Environmental Protection Agency's website. Sure enough, many of the motorcycles are listed as discharging more NOX and other polluting byproducts than cars. In the EPA's test data an '07 Honda CBR600RR has an average of 0.08 g/km NOX over the various tests. A Lincoln Navigator, in comparison, shows 0.02 g/km for the same byproducts. Carbon monoxide, another smog-producing byproduct, is listed at between 1.7 and 2.4 g/km for the CBR, between 0.6 and 0.8 g/km for the Navigator.
There are several factors that allow cars and trucks to have fewer harmful emissions than motorcycles. All the required hoses, canisters and catalytic converters fit relatively easily under a car's hood, but not so nicely on a motorcycle. That paraphernalia adds cost and weight, which is more of an issue on a $10,000, 450-pound motorcycle than a $25,000, 3000-pound car. And catalytic converters generate a lot of heat, which can be dangerous as well as uncomfortable when they are exposed on a motorcycle as opposed to tucked away underneath a car. Whatever the reasons, the EPA and CARB regulations are more lenient for motorcycles, and as a result motorcycles do emit more smog-producing pollutants than cars.
But the emissions data is just a small part of the overall impact each vehicle has on the environment, and I don't think the situation for motorcycles is as bad as it's depicted in that data alone, or as glum as it's laid out in the Times article. Primarily, the carbon dioxide emitted by each vehicle must also be considered. CO2 is a product of combustion rather than a byproduct, meaning it is a direct result of the fuel burning. A vehicle that uses less fuel will produce less CO2, and as global warming becomes increasingly important, more emphasis is being placed on fuel consumption and carbon dioxide emissions. It's safe to say that since motorcycles are, in general, more fuel efficient than cars-and especially SUVs-their CO2 emissions are less. In that respect, cars pollute more than motorcycles.
One aspect not considered in the story is how emissions data relates to real-world driving conditions. The EPA measures emissions on a dynamometer using set criteria representative of a mixture of city and freeway driving. But during a typical Los Angeles commute most cars are idling along, no doubt spewing more bad gases than indicated by the EPA's data. Meanwhile, motorcyclists are allowed to split lanes, keeping their emissions more representative of the testing procedures. On top of that, more motorcycles on the road means fewer cars, reducing congestion for everyone and, in turn, improving the automobiles' emissions. Certainly these aspects may not be enough to offset the additional pollutants that motorcycles add to the atmosphere, but they improve the situation, perhaps considerably.
Consider the tradeoffs: Yes, motorcycles generate more smog-producing pollutants than the average car. But they use less fuel, dump less carbon dioxide into the atmosphere and reduce congestion for everyone. I'm pretty confident that when I ride to work I'm doing less damage to the planet than most of the cars on the road. It's frustrating that the local paper in a city that suffers some of the worst traffic problems in the country put a lopsided view on the topic when it should be doing more to encourage alternative transportation. I'm all for reducing pollution and saving the planet, and it's unfortunate that motorcycles do pollute more than cars in some ways, but let's be realistic: Motorcycles are more a part of the solution than a part of the problem.