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There: are two;different fuel economy estimates ,for each vehicle., one for.
city driving and one for highway driving
...
To develop these
two .estimates,.
;
separate tests .are used to represent typical everyday city and rural
driving.
The test used to determine the city
fuel economy estimate simulates a
7.5 mile (12
km),
stop and go trip with. an average speed of 20 mph
(32 km/h). The trip takes 23, minutes and: has 18 stops. About one fifth
of the time is spent idling, as in waiting at traffic lights or in rush hour
traffic. Two. kinds of engine starts
are
used: a cold start, which is similar to
starting a car in the morning after it has been parked all night and a
hot
start, which is similar to restarting a vehicle after it has been warmed up,
driven and stopped for a short time.
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The test used to determine the highway fuel economy estimate represents
a mixture of "non-city" driving. Segments corresponding to different
kinds of rural roads and interstate highways are included. The test
simulates a 10- mile (17
km) trip with an average speed. of
48
mph (77
km/h). The test is run from a hot start and has little idling time and no
stops.
To assure that the fuel economy numbers are most useful for consumers,
the EPA adjusts. these .laboratory test. results. to account for the difference
between controlled laboratory conditions and actual, driving on
the road.
The laboratory fuel economy results are adjusted downward to arrive at
the estimates on the fuel economy window sticker and the
G a s
Mileage
Guide. The city estimate is lowered by 10 percent and the highway
estimate is lowered by 22 percent from the laboratory test results.
Experience has proven that these adjustments make the mile:age
estimates-correspond more closely to the actual fuel economy realized by
the average driver.
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