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3A. Sites on the same road as a Level 1 or 2 site and
3B. Other sites.
The assignment of sites to classification levels is independent of their assignment on the basis
of WIM data. Thus, it may be practical to collect Level 1 classification data at some sites for
which only Level 2 weight data are available and vice versa.
3.2 Data Produced for the Pavement Design Guide
Software
TrafLoad produces a moderate amount of traffic data for Level 1, 2, and 3A classification sites
and a very limited amount of data for Level 3B classification sites. Brief summaries of the data
produced for these two categories of sites are presented below, and more extensive discus-
sions of the data required by TrafLoad for each of the levels are presented in subsequent sec-
tions of this chapter.
Level 1, 2, and 3A Classification Sites
The most important data produced by TrafLoad's analyses of classification counts are esti-
mates of annual average daily traffic by VC, or AADTi, where the subscript i denotes VC. The
VCs may be the standard FHWA truck and bus classes (Classes 413) or any smaller set of
user-defined classes into which the FHWA classes can be unambiguously mapped. (For exam-
ple, the user may define "short," "long," and "very long" length classes, mapping FHWA
Classes 47, 812, and 13 into the three length classes.)
For Level 2 and 3A sites, TrafLoad produces estimates of AADTi by direction. However, for
Level 1 sites, at the user's option, TrafLoad will produce estimates of AADTi by lane or by
direction. When provided with AADTi by direction, the Pavement Design Guide software
applies a lane distribution factor (LDF), which is a function of the number of lanes, to estimate
AADTi for the design lane. Users of the Pavement Design Guide software may either provide
the LDFs or allow the software to use its own default values.
If the user requests estimates of AADTi by lane, the user must identify the design lane (or lanes)
and pass the appropriate data to the Pavement Design Guide software. If the Pavement Design
Guide software is told that it is receiving AADTi for a single lane, then it uses these values with-
out further adjustment. This alternative will enable the Pavement Design Guide software to use
better estimates of design lane AADTi, provided that the user is able to readily recognize the
design lane (as is frequently the case) and provided that the actual lane distribution of heavy
vehicles is not expected to change as a result of the highway improvement. (Reasons for a
change in lane distribution include adding lanes or eliminating badly deteriorated pavement
that is affecting the pre-improvement lane distribution). When these conditions do not hold,
the user should request that TrafLoad produce estimates of AADTi by direction.
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