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TABLE 1. SELECTED SOURCES OF INFORMATION PERTAINING TO

VARIOUS CONSUMER PRODUCT CATEGORIES

PRODUCT CATEGORY

ORGANIZATION

Tires

Home Appliances (refrigerators,

freezers, dishwashers, washing machines, dryers, air conditioners)

Consumers Union
U.S. Department of Transportation
General Services Administration
Tire Industry Safety Council
National Tire and Retreaders Assoc.
Tire Companies (Goodyear, etc.)
Consumers Union
Good Housekeeping Institute
R.H. Macy's and Company
Association of Home Appliance Manu-

facturers
U.S. Department of Agriculture
Bureau of Census
General Services Administration
Department of Defense
Sears Roebuck and Company
Public Utilities (Potomac Electric

Power Co., etc.)

fPotomac

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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

than quantitative.
b. The available quantitative data cover only a limited

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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
depreciated over a short time span for a specific

project.)

e.

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.

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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
also varied, ranging from information which clearly quali-
fied the existing data (e.g., for construction equipment)
to that which is collected on an intermittent basis as part

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.

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TABLE 2.

GUIDE FOR SELECTING DEPRECIATION PERIOD BASED ON

APPLICATION AND OPERATING CONDITIONS

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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

sentative,

2.1.2 Tires

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

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