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

8.0 Analysis of Vehicle Miles of Travel
of the 5-Axles or More Truck Fleet
This section provides a comparison of the mean vehicle miles of travel (VMT) for 5-axles or
more trucks.
8.1 Analysis Structure
The vehicle miles of travel (VMT) analysis evaluated the mean VMT for 5-axles or more trucks
# 8 vehicle groups (See Section 2.2)
# 11 major body type groups (collapsed from the 26 detailed body types) :
- platform (which consists of low boys and basic platform types)
- van (which includes multi-stop, basic enclosed, drop frame, insulated nonrefrigerated,
insulated refrigerated, and open top types)
- auto transport
- dump truck
- grain bodies
- garbage truck
- livestock truck
- pole, logging truck
- tank truck, dry bulk
- tank truck, liquids or gas
- other (includes platforms with devices permanently mounted, beverage truck,
utility truck, winch or crane truck, wrecker, service truck, yard tractor, oilfield
truck, concrete mixer, and other)
8.2 Mean Annual VMT by Major Truck Configuration
Figure 8.2-1 shows a comparison of the mean annual VMT for the 8 major vehicle groups for
1987, 1992 and 1997. Table 8.2-1 provides a summary of the means for the vehicle groups, the
11 body types, and various vehicle group/body type combinations. Caution should be used in
interpreting this data because of the small samples analyzed for given cases. Table 8.2-2
summarizes the number of sample records used to generate the different cell means. Statisticians
have a basic rule that if the sample size is less than 30, no statements can be made. We also feel
that caution should be used in interpreting means based on a sample size of less than 100 given
the large population this sample represents.
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