Analysis of the Vehicle Inventory and Use Survey for Trucks ... - About

2.0 Categorization of Vehicles
For analysis and for interpretation of data in terms of TS&W issues, trucks were placed into
different categories based on their vehicle configuration class, vehicle group, and state of
registration. These categories are used throughout this report to illustrate the VIUS data.
2.1 Vehicle Configuration Classes
Based on vehicle information provided in the survey, the Bureau of the Census placed each
registered truck into a configuration class. The configuration class identifies the way in which
the truck is most often operated. ‘Most often’ is a subjective term used on the VIUS survey
which has no quantitative number associated with it, such as percent of VMT. Because of this,
any interpretation of the VIUS data should use discretion. In addition, some of the analyses may
be misleading if interpreted incorrectly. For example, our analysis of commodities is based on
the percent of VMT that a particular vehicle configuration hauls various commodities. Some of
the commodities hauled by a particular truck may not be hauled in the vehicle configuration/body
type that the truck usually travels in (e.g., an auto transporter hauling farm products). However,
to conduct the analysis it must be assumed that a particular truck hauls all its commodities in the
configuration identified with it.
From responses on the survey, each truck was classified by the Bureau of the Census into a
vehicle configuration class based on 3 factors. The first factor was vehicle type, which classified
a truck as a straight truck not pulling trailer, a straight truck pulling trailer, a truck tractor (power
unit) pulling trailer, or other. The second factor was the total number of axles on the
truck/tractor. The third factor was the number and kind of trailers most often hauled, including
the number of axles. This classification scheme used survey responses to questions 5, 6 and 10.
Upon examination of the data, vehicles were placed in one of the five major vehicle
configuration classes, which was a general categorization into truck or truck+trailer combination
groups. The five vehicle configuration classes were partitioned into 31 subclasses based on the
number of axles on the truck unit and the number of axles on the trailer(s). The labels of the
subclasses are interpreted as follows: the first number represents the number of axles on the
power unit, the second number defines the number of axles on the first trailer, a third and fourth
number represent the number of axles on the second trailer and the third trailer, respectively.
Subclass names with an * by a number, N, indicate that this subclass includes vehicles with Naxles
or greater (e.g., 2+*3 subclass contains all 2-axle straight trucks pulling 3-axles or more
trailers).
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