3. Highway Motorcycles
The U.S. motorcycle fleet encompasses a vast array of types and styles, from
small and light scooters with chainsaw-sized engines to large and heavy models with
engines as big as those found in many family sedans. In 2006 approximately 850,000
highway motorcycles were sold in the U.S., reflecting a near-quadrupling of sales in the
last ten years. Even as motorcycles gain in popularity, their overall GHG emissions
remain a relatively small fraction of all mobile source GHG emissions. Most
motorcycles are used recreationally and not for daily commuting, and use is seasonally
limited in much of the country. For these reasons and the fact that the fleet itself is
relatively small, total annual vehicle miles traveled for highway motorcycles is about 9.5
billion miles (as compared to roughly 1.6 trillion miles for passenger cars).161
The Federal Highway Administration reports that the average fuel economy for
motorcycles in 2003 was 50 mpg, almost twice that of passenger cars in the same time
frame. However, motorcycles are generally designed and optimized to achieve maximum
performance, not maximum efficiency. As a result, many high-performance motorcycles
have fuel economy in the same range as many passenger cars despite the smaller size and
weight of motorcycles. Recent EPA emission regulations are expected to reduce fuel use
and hence GHG emissions from motorcycles by: (1) leading manufacturers to increase
the use of electronic fuel injection (replacing carburetors); (2) reducing permeation from
fuel lines and fuel tanks; and (3) eliminating the use of two-stroke engines in the small
scooter category.
There may be additional opportunities for further reductions in GHG emissions.
Options available to manufacturers may include incorporating more precise feedback
fuel controls; controlling enrichment on cold starts and under load by electronically
controlling choke operation; allowing lower idle speeds when the opportunity exists;
optimizing spark for fuel and operating conditions through use of a knock sensor; and,
like light-duty vehicles, reducing the engine size and incorporating a turbo-charger. The
cost of these fuel saving and GHG reducing technologies may be offset by the fuel
savings realized over the lifetime of the motorcycle.
We request comment on information on what approaches EPA should consider
for potential further reductions in GHG emissions from motorcycles. We also request
comment and data regarding what technologies may be applicable to achieve further
GHG reductions from motorcycles.
), just pointing out the request for comments.
