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TABLE 1. SELECTED SOURCES OF INFORMATION PERTAINING TO
VARIOUS CONSUMER PRODUCT CATEGORIES
Home Appliances (refrigerators,
freezers, dishwashers, washing machines, dryers, air conditioners)
Power Co., etc.)
The analysis of the data obtained and the development of re
lationships between product durability and those factors which impact upon it were found to be within the scope of traditionally employed statistical methodologies. However, the use of these methodologies is expected to be restricted over the short-run because of various problems
associated with the available data base. These problems are of the following form:
a. Most of the available data are qualitative rather
operated are not always known and are not uniform.
for comparison purposes across the product category.
d. The stated in-service period for a particular pro
duct does not necessarily reflect its true useful
life; (e.g., some heavy construction equipment is
Maintenance records, repair records and associated
costs are not usually available for most products.
The form and nature of currently available data are discussed
next. An analytical treatment, illustrating the use of various statistical techniques, is also presented.
2.1 Data Acquisition
As stated above, data were not availal
for all of
the study product categories and, of those which were
available, not all were quantitative in nature. The form
of consumer surveys, and is therefore of inferential value.
These data characteristics (nature and form) are described
for the following product categories
2.1.1 Heavy Construction Equipment
Of all the product categories studied, we found that
the best information and data existed for heavy con
struction equipment. This information is well docu
mented by various manufacturers and is intended pri
marily for use by contractors in their development
of operating costs and depreciation rates for equip
ment for specific projects. For example, Table 2
presents the estimated depreciation period* for various types of construction equipment according to appli
cation and operating conditions. A similar analysis
for tire life, for a particular type of equipment,
* This period is not necessarily equivalent to physical life.
i.e., motor graders, is shown in Figure 1. The com
bination of these data elements with information per
taining to repa ir factors based on specific operating
conditions (Table 3) permits the development of estimated owning and operating costs. Table 4 is an example of the way in which these data are used in esti
mating such costs for a track-type tractor.
A summary of average physical life, for various major
types of construction equipment, as estimated by con
tractors and equipment distributors is presented in
Table 5. Although these estimates are based on a
1963 survey, it is believed that they are still repre
There are several variables which have a marked effect
on the performance and durability of tires. These
variables include both the type of construction and
kind of materials used. For example, the ply, tread width, rubber composition, and nature of accessory material (nylon, polyester, steel) are all important influencing factors. Also, there is a demonstratable trade-off between performance and durability whereby materials that display better gripping characteristics result in concessions in terms of tread life. Currently