Transport Partnership
U.S. ENVIRONMENTAL PROTECTION AGENCY
A Glance at
Clean Freight Strategies
itomatic Tire Inflation Systems
Automatic tire inflation systems can save tire maintenance costs and improve fuel economy by nearly 1%, saving
100 gallons of fuel and eliminating one metric ton of greenhouse gas emissions per year. Properly inflated tires
also wear longer and have fewer punctures.
What is the challenge?
When not properly inflated, tires flex more under
load, producing heat and increasing rolling
resistance, which wastes fuel. Truck tires inflated ten
pounds per square inch (psi) below recommended air
pressure levels can reduce truck fuel economy from
0.5 percent to one percent. Heat and stress from
improper inflation soften and deflect tire components,
causing faster and more uneven wear, which
shortens the life of the tire. Under inflated tires have
more frequent punctures, increasing the risk of tire
failures that could lead to costly road service and loss
of revenue.
Despite these costs, a recent survey of combination
trucks found that less than half the tires surveyed
were within five percent of the recommended inflation
pressure. Fleets may find it difficult to keep tires
properly inflated since truck tires can lose up to 2 psi
each month, even if the rim seal and valve stems are
tight. This is because air molecules can permeate
through tires. Temperature and load also affect tire
pressure. For these reasons, tire manufacturers
recommend checking tire pressure each week and
establishing a tire maintenance program.
Even a good tire maintenance program may fall short
of its aims. In part, this is because trailer tires have
more impact on truck fuel economy than tractor tires,
yet trailers are interchangeable and thus harder to
monitor. Since the bulk of the load is carried in the
trailer, a 10-psi under inflation in a trailer tire may
have nearly twice the impact on truck fuel economy
as the same amount of under inflation in a drive tire.
Despite the importance of keeping trailer tires
properly inflated, a fleet may not be able to inspect its
trailers regularly. A trailer may be gone from the
service yard for extended periods of time while on the
road, at a customer's facility or at drop-off location
waiting for a back haul. A fleet may not even own the
trailers it hauls, but pick them up from a shipper or
third party. These circumstances can place much of
the responsibility for checking tire pressure onto
drivers. However, one industry survey indicates only
eight percent of truck drivers check tire pressure with
a tire gauge before each trip.
What is the solution?
Automatic tire inflation (ATI) systems monitor and
continually adjust the level of pressurized air in tires,
maintaining proper tire inflation automatically, even
while the truck is moving. One ATI system uses the
vehicle's own air-brake compressorto supply airto all
the tires. Another system uses self-contained
compressors mounted on each hub that are powered
by the rolling motion of the wheels. Once an ATI
system is installed, it should not require any special
attention from the driver.
The results are in ...
ATI systems can extend tire life by eight percent or
more. The systems eliminate the need to check tire
pressure manually, saving time and labor while
ensuring consistent and proper tire inflation. Installing
an ATI system on a truck's drive axles and trailer
costs up to $900, but can save over $200 annually in
tire maintenance costs. For a typical long-haul
combination truck, annual fuel savings could reach
100 gallons, saving $170 in fuel costs and eliminating
one metric ton of greenhouse gas emissions. The
cost of installing an ATI system in a line-haul truck is
generally recouped in just over two years through
fuel and maintenance cost savings. Truck fleets may
realize additional savings from reducing the risk of
expensive tire failure caused by under inflation.
Next steps
Line-haul carriers that find it too difficult or expensive
to monitor tire pressure on a regular basis should
consider installing automatic tire pressure inflation
systems on drive and trailer tires. ATls can be readily
retrofitted onto existing trucks and trailers. Interested
fleets can check with ATI manufacturers and truck
and tire dealers for more information. Fleets may also
contact tire manufacturers or their state or national
trucking associations for more information about the
benefits of proper tire inflation.
U.S. Environmental Protection Agency 4) Office of Transportation and Air Quality
.uary2004. EPA420-F-04-01O. 0 For more information,, visit: www.epa.gov/smartway
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