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

Table 2.1-1 The 5 Major Vehicle Configurations and the 31 Subclasses
Truck Truck & Trailer Tractor-Semitrailer Tractor + Doubles Tractor + Triples
S2
S3
S4
2 + 2
2 + *3
3 + 2
3 + *3
*4 + 2
*4 + *3
2-S1
2-S2
2-*S3
3-S1
3-S2
3-*S3
4-S1
4-S2
4-*S3
5
2-S1-2
3-S1-2
2-S2-2
3-S2-2
other @ *7-axle
3-S2-3
other @ *8-axle
3-S2-4
other @ *9-axle
other @ *10-axle
2-S1-2-2
3-S1-2-2
other
Notes:
- A semitrailer is classified by S and its number of axles (e.g., S2 means a semitrailer
with 2 axles).
- The * means "equal to or more" (e.g., *4 + 2 means a straight truck with "4 or more"
axles pulling a trailer with 2 axles).
- Even though the survey only asks the total number of axles on the attached trailers, the
configuration type can be more clearly defined based on operational practice.
2.2 Vehicle Groups
In the analysis of the 5-axles or more fleet, trucks were categorized into 8 vehicle groups (see
Figure 2.2-1 for pictures of various configurations in each group):
# Truck + Trailer with 5-axles (which contains vehicle configurations 2+*3 and 3+2)
# Truck + Trailer with 6 or more axles (which contains 2+*4, 3+*3, *4+2, *4+*3)
# 3-S2 Tractor-Semitrailers
# Tractor-Semitrailers with tridem axles (which contains 2-*S3, 3-*S3, 4-*S3)
# Other Tractor-Semitrailers (which are 4-S1 and 4-S2)
# STAA Tractor+Double Trailers (which is 2-S1-2)
# Tractor+Double Trailer combinations with 6 or more axles
# Tractor+Triple Trailers.
It should be noted that a small number of trucks may be misclassified into the wrong vehicle
groups. For instance, the tridem axle tractor-semitrailers may contain a few records for vehicles
hauling a trailer with more than 3-axles. The reason for this is that the survey question on the
number of axles on the semitrailer was limited to 3 responses with the last category being “3 or
more axles.”