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Motorcycles Emit “Disproportionately High” Amounts of Air Pollutants

Emissions ratios from two-wheelers and cars in the Swiss fleet. A number >1 indicates more emissions from the two-wheelers. Click to enlarge.

Motorcycles collectively emit 16 times more hydrocarbons, three times more carbon monoxide and a “disproportionately high” amount of other air pollutants compared to passenger cars in the Swiss fleet, according to a Swiss study to be published in the Jan. 1 issue of the American Chemical Society’s journal Environmental Science & Technology.

The study, by Ana-Marija Vasic and Martin Weilenmann of the Swiss Federal Laboratories for Materials Testing and Research, found both two- and four-cycle motorcycle engines emitted significantly more of these pollutants than automobile engines.

The researchers measured exhaust emissions of CO, HC, NOx, and CO2 from eight two-wheelers and compared them to previous measurements from 17 gasoline-powered Euro-3 compliant passenger cars performed at EMPA with the aim of ascertaining their relevance.

Several comparisons show that the powered two-wheelers on the market in 2001 produced significantly higher emissions of all pollutants except CO2 than gasoline-powered passenger cars from the same sales period. Whether in a direct comparison of mean unit emissions (in g/km), mean yearly emissions (in kg/vehicle/year), or fleet emissions (in tons/year) [calculated for the Swiss vehicle fleet], the two-wheelers’ HC and CO emissions were all, and often significantly, higher. In addition, the NOx contribution of the motorcycle fleet is roughly one-fifth that of the car fleet and is thus not negligible.

Motorcycles aren’t a primary means of transport in most developed countries, the authors note. As a consequence, they say, the importance of [motorcycle] emissions has been underestimated in legislation, giving manufacturers little motivation to improve aftertreatment systems.

Even though the motorcycle fleet is small in comparison with the car fleet, and logs lower yearly mileage per vehicle, their contribution to traffic emissions has become disproportionately high.

Present-day aftertreatment technologies for motorcycles are not as efficient as those for cars. Until recently, for instance, US emission standards for highway motorcycles hadn’t been updated in 25 years.

That regulatory situation is about to change, but more attention is required, according to the authors.

Even if they account for a comparatively small number of vehicles, motorcycles’ impact on traffic emissions cannot be overlooked. Directive 2002/51/EC of the European Parliament and Council is a step in the right direction. With the introduction in 2006 of new emissions limits which are intended to correspond to Euro 3 gasoline cars, and with checking procedures for the correct operation of emission control systems, motorcycle emissions are expected to decrease.

However, the fact that more than half of the two wheelers [in the research] failed the statutory test is indicative of the need for periodical inspection and maintenance.

With regard to this study, the introduction of similar regulations as for passenger cars such as checking the durability of the aftertreatment system and periodic testing of exhaust gases should be considered. It would therefore be expedient to repeat this study two to three years after introduction of the new rules.




2-stroke engines should be banned worldwide. Period. Hopefully the increasing gasoline cost will make 4-strokes more attractive (even if more expensive initially).


The vast majority of motorcycle engines are 4 stroke. In fact, you'd be hard pressed to find a street legal, roading going 2 stroke. The last one I can think of is the Aprilla SR 50, and you couldn't ride it enough to make a difference anyway.

Jon Abbott

I primarily ride motorcycles for higher fuel efficiency, but did not know much about their emissions until now. I know motorcycles sold in California require special emission system modifications (like in cars there), but not so in the other 49 states... Glad to see that CO2 and NOx emissions are much lower for motorcycles, despite the other issues. Thanks for posting the article!



Actually their NOx emissions ARE very high.

From the article:

In addition, the NOx contribution of the motorcycle fleet is roughly one-fifth that of the car fleet and is thus not negligible.


I looked into motorcycles and found they dont get the good mpg you would imagine. Most do 50mpg. Many do less. So there are cars that get similar mpg to a bike, like an Insight, Prius or certain diesels. Mothercycles are (or can be) much cheaper, faster, more fun, easier to Park, but the mpg is not as amazing as you would imagine.


Even 4 cycle engined bikes are polluting like crazy and they dont get as good of milage as many expect.

Some bikes get worse gas milage then a full sized sedan.


A few years ago I was camping and talked to a couple who were touring on a Honda Goldwing trike with a tent trailer.  Cute rig, but the owner told me that he got something like 25 MPG (exact figure forgotten) punching into the winds we'd been seeing.  My car, much bigger, heavier and far safer, was getting better than that.  (But I didn't look as cool.)

Motorcyles are mostly about speed and style.  If you really want economy, you can get a Honda Insight or persuade someone to commercialize something like the Lean Machine.


I don't think anyone rides a goldwing to save gas. That thing weighs 1000 lb. It shouldn't even be considered a motorcycle.


Actually their NOx emissions ARE very high.

From the article:

In addition, the NOx contribution of the motorcycle fleet is roughly one-fifth that of the car fleet and is thus not negligible."

Actually no. That statistic was about the Swiss fleet of vehicles which has absolutely nothing to do with the situation in our country.

If we start requiring heavy emissions controls on motorcycles it will murder every small producer. I know some people on here want to pursue any reduction in pollution with fanatical zeal. It will just push more business into the hands of a few large corporations. The same thing happened to the US auto industry and look where that got us. A couple of giant lobbies that tell us we should all drive giant SUVs, burn lots of cheap gas and build more highways. Sometimes a fragmented the market is a good thing. I'm not saying motorcycles shouldn't have emissions controls on motorcycles. But the way we go about it in this country is Draconian and it only benefits the big players.


Goldwings weigh something like 900lbs and are about the biggest motorcycles you can get. They have a 1.8L six cylinder engine, HUUUGE for a motorcycle. It's the "S-class/760iL" of motorcycles. They have built in radios and for 2006 they even come with an airbag.

I owned a 2001 Yamaha YZF600R motorcycle for a couple years. It was a "race replica"/sportbike (aka crotchrocket) and had a 599cc (.599 liters/36.4 cubic inches) four stroke inline four cylinder engine. If I rode it at the same speeds (accelerating the same rate) as I do in my Ford Ranger it would EASILY get 60mpg...EASILY! Now if I rode it so I out accelerated every car in traffic 100% of the time (still not working the bike hard at all) I would get 45-50mpg NO problem what so ever. If I rode the bike like a bat out of hell and really got on it, I'd still get 40mpg...and I'd REALLY have to work at it to get to go below 40mpg.

Now if you flog a new 1000cc sportbike around a race track you'll probably see 30mpg, but riding at a sane pace on the street you'll get 35-45mpg usually. Not bad for something that can do the 1/4 mile in under 10 seconds (100% stock too) with a good rider who knows how to drag race.

If you ride casually (not fast, at a leisurely pace) on a Harley Sportster you probably see 45-60mpg. There are several full size motorcycles with single cylinders out there that are great for commuting and can get 60-80mpg.

Remember motorcycles are fun to ride and are usually viewed as toys. When people get on them they usually go a lot faster than they do in their cars, which hurts their mpg. They also have small tanks and it's harder to measure your mpg and get good consistant figures.

A new 600cc sportbike can do the 1/4 mile in under 11 seconds at the drag strip and give you 50mpg on your way there and back. A new corvette will do it in just over 12 seconds and might get 20mpg. You can buy a used literbike that'll do the 1/4 mile in the 10s and still give you 40mpg for as little as $5k, I doubt I'll ever see a car for $5k with that kind of performance (both acceleration and mpg).


Funny, my friend who owns a 550cc bike was getting about the same mileage out of it (35 MPG) as I got in my old VW.  $5/gallon fuel would have hurt him just as badly as me.

My new VW (bigger, much safer) hurt me on the last tank - it delivered 36 MPG instead of my usual 39+. ;-)

Doug Hawley

I am perplexed at the constant reference to the Honda Insight. Only 9 sold in Canada last YEAR and I think less than 100 in the USA. No Honda dealer will stock them as they don't expect to sell any.

The 2001-2006 Goldwing has emission control that qualifies to the Calif. 2008 standard. The Swiss study is only looking at the 2001 motorcycle fleet and does not reflect the more recent 2005-6 fleet upgraded with cataylists and careful fuel injection mapping. They are trying to beat a horse that has long left the barn.


The Insight gets better mileage than most motorcycles, carries two people in comfort and offers crash protection too.

Dave Zeller

I am curious about the overall demographics of the motorcycle fleet "studied" by The Swiss Federal Laboratories. The primary demographic to which I refer is the overall age of thse motorcycles.

Many people in both Europe and the United States ride very old motorcycles. Classic machines such as Harley-Davidson, BMW, Moto Guzzi, Ducati, Royal Enfield, and the orphan bikes from long extinct manufacturers tend to have very long product lives as many of them were designed with a capability to be recycled and rebuilt many times over,unlike modern transportation machines.

Many a rider in Europe bought a motorcycle with the intent of riding it many, many years, as the cost of living there seems to impede the frequent purchases of newer technology incorporating fuel injection, ignition-control computers, and other such things.

I myself ride a modern Ducati, which due to its modern technology can be rather peculiar in its need for expensive routine dealer maintenance. I can understand why many riders prefer a motorcycle that they can easily repair themselves, and thus take pride in. You cannot buy a modern motorcycle, with the exception of a Royal Enfield or Ural, that can be owner-maintained and repaired.

Lately, there has been much hot discussion among Europeans concerning the plague of anti-motorcycle regulations proposed by the E.U., which if inacted would essentially ban ANY and ALL motorcycles by 2020.

I shall speculate that if one was to look into this Swiss "study", one would probably see many of the E.U. prejudices incorporated in this report by a FEDERAL laboratory. In other words, a flawed "study".

Can anyone really expect a properly ordered, unopinionated study sponsored by any agency mandated by Government fiat?


Bikes can be very confusing in terms of fuel economy because of several factors. First, the primary factor is the engine size. The rough border is 500cc and bigger engines on sport/cruising bikes are for performance machines that are designed for fun and therefore have a poor efficiency - as bad as cars. However 500cc and smaller engines are designed for efficiency and other priorities (comfort) and achieve at least 50 mpg, can go as high as 100 mpg. Note that these are not fast machines, may have a limited range (city riding) and generally get much less attention than the more poweful super sports. So you can have 200cc - 300cc that can compete with Prius and Insight as well as 1100cc monsters that are worse than most cars and even some SUVs.

Second, riding style just like driving style affects efficiency. A leisurely ride on a 700cc cruiser can still achieve a decent mpg, say around 40 give or take. Unfortunatelly, many riders want to have fun and demand maximum power at all times which is obtained at a higher RPM. For super sports that would be around 10,000 RPM and more. I have met many riders who ride at such a high RPM all the time and simply don't care about efficiency. In those cases they will get a much lower MPG. The typical scenario is a 600cc super sport cursing at around 10,000 RPM which would yeidl around 25-30 MPG, comparable to a regular car.

In summary, since many/most MC owners ride for run they tend to have larger engines (600cc+) and use higher RPMs resulting in a very poor efficiency. These are simply choices people make.

The minority chooses smaller engines (less than 500cc) and don't pop wheelies ;) They get 50 MPG and more.

As for me, on my 600cc Kawi riding nicely (slow acceleration and gentle breaking, anticipate red lights, etc.) I get 5 l/100 mk, which is around 55 MPG I think.

In the end it comes down to people and their choices.


re: the motorcycles in the study.

The motorcycles were FAV 3/Euro 1, corresponding to the Euro 3 passenger cars.

1998 Yamaha YN50
1996 Piaggio Skipper
1997 Piaggio Vespa
1996 Yamaha Yp 250
1993 Honda Shadow
1993 Suzuki VS 800 GLP
1998 Honda VFR 800 FI
1999 BMW R1150GS


Doug, Honda loses money on every Insight they sell (even for 2006, the models 7th year...came out in 2000). According to the recent sales figures I've seen reported they sold about 700 in the US for 2004 and will probably sell 700 again in 2005. Honda is perfectly fine with them selling at that rate. They just want the top spot on all the MPG charts, it's the only reason why they keep the Insight around. It doesn't help it's sales numbers that's only a 2 seater either.

Dave, the expensive maintenance for your Ducati has nothing to do with it's modern technology and everything to do with it's desmodromic valve train. TONS of new bikes can be owner-maintained and repaired just as they have been in the past. If someone wants to take the time and feel confident in their wrenching ability they can even adjust the valves on a Ducati in their garage...but they're a minority as most people don't want to do their own maintance. Bikes have gotten more complex but they're still relatively easy to work on, however the average biker has changed and more of todays bikers would rather pay a stealership to maintain their bike than to learn how to do it themselves.

Bob, 1100cc monsters that get worse gas milage than most cars and even some SUVs? I'd like to know what specific bikes you're talking about lol. The only one I can think of would be a Boss Hog (which has a Chevy 350 V8). The least fuel efficent sportbike I know of is Honda's RC51, even when racing one around a track you'll still see 25-30mpg....better than the average new car which I think is around 24mpg? But you're right on about medium to large motorcycles being designed for performance only and that they just happen to get decent-good mpg. 600cc supersport gets 25-30mpg while cruising? I don't think so, not even a Honda supersport. Also 10,000 rpms is a pretty high for "cruising".

Wow a couple bikes from 1993, they're really going back. The '98 VFR800 I don't believe was "FI" (fuel injection), few bikes were back then....most cars have had FI since what the late 80s? I doubt any of those bikes had catalitic converters either, cars have had those for atleast a couple decades now. TONS of new cars have some kind of variable valve timing, I know of only one motorcycle that currently has it ('02+ Honda VFR800). A lot of higher end cars today have variable intakes/intake tracts, only one production motorcycle has anything like that and it's a $40,000 Italian sportbike.


I used to want to ban all two strokes as well, but many advances have been made, mainly in the field of outboard boat engines. There are now two-cycles that are as efficient and clean as any four-stroke from Honda. These are recent improvements, last two or three years ago.

Still, my '79 rabbit diesel gets twice the mileage as my wife's subaru, and is more fun to drive. Running on biodiesel, it puts out less emmissions per mile as well. Still not perfect - there's no cat converter or equivalent - but I feel pretty good about driving it.



I probably did exaggerate and numbers are probably off.
The survey on my board had several bikers saying they get about 200 km on a tank, which is usually around 15 liters. That would be around 30 mpg.

Regarding 10K RPM, consider the typical 600cc super sport rider out to have fun:
1) hard acceleration/breaking
2) pop some wheelies
3) fast passes

Sure, 10K RPM is not unusual. Wanna hear my pipes? Here, let me rev it some ;) Really, some riders look for any excuse to rev higher.

Overall my numbers are probably off some. Still, the average rider will get similar MPG to many average size cars, which doesn't make sense (as bikes have a single passanger and are might smaller/lighter).


I think your idea of an "average size car" and the "average car in america" might be different? You're using kilometers and liters, are you in Europe? Canada? US cars and canadian cars are pretty similar but the average car in europe gets a lot better gas milage than the average car in the US. The average mpg for all new cars sold in the US in 2004 was just 24.6 mpg according to this Washington Post story...

I would guess the average mpg for new cars sold in Europe is over 30mpg? I think the average mpg for motorcycle riders is over 40mpg. Even if I did a lot of the 3 things you listed on a supersport I think I'd average 40mpg. No doubt some jackasses rev their bike higher for no reason, but even then someone is going to have to go out of their way to get below 35mpg on a 600 I think. Yes bikes generally have a single passanger but for the most part cars carry just one person most of the time too (probably different to some degree in other countries).



Sorry, should have explained my context.

North America, Canada

The current trend here is to build bigger engines. Even the "small cars" here (by North American standards) have at least 2,000cc engines. For example, my old Honda Civic 1995 has 1600cc, while the newer Mazda Protege is 2000cc and I have a hard time finding cars with less than 2000cc. So the "average car" in Nort America has very poor efficiency, like you said 25 MPG.

As for bikes, you have 2 categories. Those who ride to work (bike for utility) get 40 MPG and often better. They will generally have 600cc or smaller engine. Those who ride for pleasure (bike for fun) have a 600cc or bigger engine and use higher revs so generally will be under 40 MPG. Even the cruisers because of bigger/heavier bikes and bigger engines would be limited to no more than 40 MPG.

Now to explain the term "fun" in the North American terms, you are cruising around 120-150 km/h on the way to the "fun part" at which point depending on skill/craziness level you are taking turns anywhere from 120 to 200 km/h. So if you are riding a 600cc SS pushing it to say 150 km/h then you easily get to 10K RPM and more. Most riders on purpose use a lower gear to get the RPM higher. Let me assure you that many of these riders easily come down to 20-30 MPG.

Note that this is just a generalization. Different people in different towns have different habits. In North America most highway speed limits are 100-120 km/h, so these speeds are common.


Just to clarify,

I don't think that motorcycles are "evil", pollute too much, etc. However, it is clear that the industry seems to be focused more on performance than efficiency. Also it is clear that riders often use them for fun with no regard for pollution.


You're right about them only caring about giving their motorcycles more performance and not concerned at all really about gas milage. If they ever designed a true "commuter" motorcycle with it's emphasis on fuel economy and with all the technology the avg new car has (not sure what the price of this bike would be though) it would easily get over 100mpg.

I still think you're off on the 20-30mpg figure for 600s when riding on the street, even if you ride how you describe. You'd have to be racing on the street to get near 30mpg on a 600 imo. I can definately believe a Goldwing only get 25mpg, which seats as many people as a corvette and is roughly as quick as one too. I don't have much experience with the big cruisers but I know several of the modern Harleys will get 40 mpg while cruising around town. Harley's Buell sportbikes with their large 1203cc are listed 48 mpg in the city and 65 mpg on the highway. You'll easily get 50mpg all day long on that kind of bike. Even if you race those bikes up and down a twisty road all day long thrashing them you'd have a hard time getting under 40mpg.

Heres a few links to, it's the biggest message board out there for Buells and people consistantly report around 50mpg for their 984cc & 1203cc V-twin sportbikes.

A thread on a sportbike board listing some decent sporty commuters...

"Here are some fuel mileage figures from Motorcycle Consumer News --

BMW F650 CS (single cylinder) -- 46 mpg
BMW F650 GS (single) -- 53 mpg
Buell Blast (single) --55 mpg
Ducati Monster 620ie -- 52 mpg
Hardley-Ableson Sportster 883L -- 51 mpg
Kawasaki Ninja 500R -- 64 mpg
Kawasaki W650 (vintage-styled twin) -- 46 mpg
Suzuki GS500 F -- 48 mpg
Suzuki DL650 V-Strom -- 48 mpg
Suzuki SV650/S -- 36/48
Honda Nighthawk 250 and Kaw Ninja 250 aren't listed, but I'd guess 60-70 for them."

"MO observed fuel milage"
ZX-10R 45.8 avg mpg (1000cc Inline 4)
955i Daytona 42.1 (955cc Inline 3)
GSX-R1000 40.8 (1000cc Inline 4)
CBR1000RR 39.2 (1000cc Inline 4)
YZF-R1 37.9 (1000cc Inline 4)
RSV-R 36.2 (1000cc v-twin)
999 34.1 (1000cc v-twin)
RC-51 32.3 (1000cc v-twin)

Gaijin Biker

Bear in mind that the Goldwing mentioned in the above comment was a trike, not a two-wheeler.

Gaijin Biker

...and pulling a trailer, at that!

Gali Goldwaser

Someone help! I am looking for the most fuel efficient MC to communte and run errands. I don't care about performance, style, or manhood. Just want to save money and have a reliable MC, without having to ride a scooter because my town is hilly. Any suggestions?

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