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'MythBusters' asks: Are motorcycles greener than cars?

September 28, 2011 |  6:01 pm

BubbleBike2A trend is afoot, according to "MythBusters" television host Adam Savage: "People are trading in their cars and driving motorcycles instead because they believe that's the more environmentally friendly choice," Savage said in Wednesday's season opener of the popular Discovery Channel show. "The logic is because motorcycles are generally more fuel-efficient than cars, they burn less gas and thus they must be better for the environment."

The question is: Are they really? As the MythBusters have done with each of the show's previous seven seasons, Savage and his co-host Jamie Hyneman set out to test the theory.

Selecting three motorcycles and three cars that represented popular models from the '80s, '90s and '00s, they put the six vehicles through a 30-minute, 20-mile course. Seventy-five percent was freeway driving; the other 25 percent was in the city. Savage drove the three cars. Hyneman trailed him at speed on each of the three bikes. None of the vehicles' makes and models were disclosed.

All of the vehicles were equipped with portable emissions-measuring systems that took exhaust gases from a probe in the tailpipe and engine information from the engine control unit.  The devices  determined the vehicles'  fuel economy and emissions profiles while the vehicles were running on the real-world course in California's Alameda County earlier this year.

The upshot? Motorcycles were indeed more fuel-efficient than cars and emitted less of the greenhouse gas carbon dioxide, but they emitted far more smog-forming hydrocarbons and oxides of nitrogen, as well as the toxic air pollutant carbon monoxide. For the most recent model year vehicles tested -- from the '00s -- the motorcycle used 28% less fuel than the comparable decade car and emitted 30% fewer carbon dioxide emissions, but it emitted 416% more hydrocarbons, 3,220% more oxides of nitrogen and 8,065% more carbon monoxide.

The MythBusters' conclusion: "At best, it's a wash. Motorcycles are just as bad for the environment as cars," Savage said on the show. "At worst, they're far worse."

"We've been working to clean up passenger vehicles since the '70s," said Kent Johnson, who's on the research faculty at UC Riverside and is director of its emissions lab, where the MythBusters' numbers were analyzed. "We've been putting on catalytic converters and sensors to improve their ability to control emissions. We didn't start doing that on motorcycles until the 2000s. It just shows you how far we've taken passenger vehicles and how difficult it is to do the same thing with motorcycles. First of all, there's no room. And the incremental cost might double the price of a bike."

The California Air Resources Board, which had been approached to perform the emissions tests for "MythBusters" but couldn't because the tests it performs are stationary, concurs with Johnson's assessment about the added cost and technology burdens of placing greater emissions controls on motorcycles.

While many modern motorcycles are now fuel-injected and equipped with catalytic converters and charcoal canisters to control emissions, they still pale in comparison to the emissions controls of cars. That point was made in a followup emissions test performed on the "MythBusters" season opener when Hyneman constructed an aerodynamic shell for a "late-model," 250-cc, single-cylinder motorcycle equipped with fuel injection and a catalytic converter.

Without the aerodynamic shell that transformed it into the so-called "bubble bike," the motorcycle achieved 56.1 miles per gallon, but it ranked second-highest for carbon monoxide emissions and third-highest for hydrocarbons and oxides of nitrogen of all the vehicles tested during the show. The aerodynamic shell increased the bike's fuel economy to 70.9 miles per gallon, but its carbon monoxide, hydrocarbon and oxides of nitrogen emissions remained stubbornly high.

"Our strategy with motorcycles has always been to control them to what's cost-effective and technically feasible, and that's always lagged behind cars," said John Swanton, air pollution specialist with the Air Resources Board. Emissions standards for motorcycles are, accordingly, more forgiving than they are for cars and will most likely stay that way since motorcycles account for such a small portion of vehicles on the road.

The Air Resources Board estimates there are 600,000 motorcycles in active use in California, which account for less than 1% of vehicle miles traveled in the state. Those 600,000 motorcycles, however, account for 13% of the state's hydrocarbon emissions from passenger vehicles, Swanton said.

"Our goal in regulating all vehicles is to retain the gains we've made in reducing smog-forming emissions because those have an immediate impact on the health of Californians. You are immediately impacted by ozone, whereas climate emissions are longer term," he said.

While 90% of internal combustion engine emissions are carbon dioxide, a greenhouse gas, "To trade one emission for another is not the best strategy," Swanton said. "We've got to balance the two."

In the 2011 American Lung Assn. State of the Air report, eight of the top 10 cities for ozone pollution were in California. Los Angeles ranked first.

Despite the MythBusters' findings, emissions are only part of the story of a vehicle's true greenness. According to the Motorcycle Industry Council, motorcycle manufacturing requires thousands fewer pounds of raw materials than automobiles. They require less fossil fuel, so they require less energy to pull that fossil fuel out of the ground. They use fewer chemicals and oils than cars. And motorcycles produced today are 90% cleaner in California than they were 30 years ago.

Note to MythBusters: How about a cradle-to-grave life cycle assessment for cars and motorcycles for the Season 9 opener? 

RELATED:

Inconvenient truths about motorcycles and smog

California considers requiring motorcycle smog checks

Gov. Schwarzenegger tells motorcyclists to pipe down, signs noise bill

-- Susan Carpenter

Photo: "MythBusters" host Jamie Hyneman tests his aerodynamic "bubble bike" on the season opener of the Discovery Channel show. Co-host Adam Savage stands in the foreground. Credit: Discovery Channel

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