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Table 1.1 Traffic Data Elements to be Produced by TrafLoad a b AADTi by direction for up to 13 VCs (i) (1, 2, and 3A) Annual Average Daily Truck Traffic (all classes, combined) (3B) c Truck Traffic Classification Group (3B) Monthly Traffic Distribution Factors by VC (1, 2, and 3A) Axle-Load Distribution Factors Site Specific (1) Axle-Load Distribution Factors Regional (2) Axle-Load Distribution Factors Statewide (3) Linear or Exponential Growth Rates d Directional Distribution Factors (1, 2, and 3A) Axle Groups per Vehicle (for each VC) Hourly Distribution Factors (1, 2, and 3A) a Annual average daily traffic by VC (i). b Numbers in parentheses identify the input levels for which the data are used. c Each Level 3B site is assigned by the user to a truck traffic clas- sification group. This assignment is passed by TrafLoad to the Pavement Design Guide software without modification. d Because all AADTi estimates will be provided separately by direc- tion of travel, all corresponding directional distribution factors for Level 1, 2, and 3A sites will be set to 1.0. TrafLoad has been designed to be the principal source of traffic data for the Pavement Design Guide software. A summary of the traffic data elements produced by TrafLoad for use by the Pavement Design Guide software is presented in Table 1.1. TrafLoad currently allows the use of the 13 standard FHWA vehicle classes (VCs) (see Table 1.2) and/or an aggregation of these classes into a smaller set of user-defined classes.3 The latter option makes it possible to develop pavement designs for sites for which vehicle classification data are available only by length class. 1.2 The Remainder of Part 2 Chapter 2.0 of Part 2 presents in some detail the development of a program for collecting the weight data that TrafLoad requires for generating axle-load distribution factors and estimates 3 The Pavement Design Guide software currently allows the use of up to 13 classes. 2-2
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Table 1.2 FHWA Vehicle Classes 1. Motorcycles 2. Passenger cars 3. 4-tire trucks 4. Buses 5. 2-axle 6-tire trucks 6. 3-axle trucks 7. 4+ axle trucks 8. 3-4 axle single-trailer combinations 9. 5-axle single-trailer combinations 10. 6+ axle single-trailer combinations 11. 5-axle multi-trailer combinations 12. 6-axle multi-trailer combinations 13. 7+ axle multi-trailer combinations of axle groups per vehicle for each VC. TrafLoad is capable of using data provided by the state to generate these values for every site for which such data are requested, though the quality of the estimates will be higher for Level 1 sites (for which site-specific data are provided) than for Level 2 or 3 sites. Chapter 3.0 presents a similar discussion of the development of a program for collecting the classification counts TrafLoad requires for generating most of the other traffic data required by TrafLoad. As indicated in a footnote to Table 1.1, all estimates of annual average daily traf- fic by VC (AADTi) for Level 1, 2, and 3B sites are produced by direction, so the corresponding directional distribution factors are set to 1.0. For Level 3B sites, no directional information is supplied to TrafLoad, so it does not produce directional factors for these sites. Instead, the Pavement Design Guide software will use its own default values. The final chapter discusses the collection and handling of the traffic data required to create the necessary datasets. 2-3