Forecasting Statewide Freight Toolkit (2008) / Chapter Skim
Currently Skimming:
Pages 9-15
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 9... ...
The Federal Highway Administration's Quick Response Freight Manual describes two methods of applying factors to traffic volumes applicable to rural highways as well as urban highways.3 The first method involves estimating a growth factor from current and past truck count data and applying the resulting factor to future years using a conventional compound interest formula. The second method determines separate growth factors for various "economic indicator variables," usually employment in local industrial sectors.
|
From page 10... ...
The socioeconomic data used in a typical truck model are consistent with those data used in Model Component Model Class Direct Factoring Trip Generation Trip Distribution Mode Split Traffic Assignment Economic/Land Use Modeling Direct Facility Flow Factoring Method Of facility flows O-D Factoring Method Of O-D tables Included Included Truck Model Based on exogenously supplied zonal activity Included Not Applicable Included Four-Step Commodity Model Based on exogenously supplied zonal activity Included Included Included Economic Activity Model Based on outputs of economic model Included Included Included Included Table 4.1. Freight model classes by component.
|
From page 11... ...
that pass through the state with both origin and destination outside the state are added to the external truck trips as well. Trip rates are applied to socioeconomic data and also are used for truck terminals and intermodal facilities in conjunction with observed truck trips at airports, seaports, and rail terminals.
|
From page 12... ...
The trip distribution component for the Florida Intermodal Statewide Highway Freight Model described in Section 8.9 uses a standard gravity model and distributes tons produced in one zone to tons consumed in another zone using friction factors calibrated based on the average trip lengths identified from TRANSEARCH. In the Indiana Commodity Transport Model described in Section 8.8, freight shipments are distributed by a gravity model calibrated using the CFS data.
|
From page 13... ...
However, there are some exceptions where the freight tonnage is divided into an equivalent number of ′ = ( )
|
From page 14... ...
In freight truck only assignments, the freight truck trip table is assigned to the highway network using an all-ornothing assignment process. Since a straight all-or-nothing assignment typically loads too many trips onto the interstate highways, a procedure to adjust the link speeds for noninterstate highway segments is often applied.
|
From page 15... ...
The Transportation Research Board's Highway Capacity Manual recommends PCE values of 1.5 and 2.0 for single unit trucks with six or more tires and combination units respectively. The truck model developed by the Baltimore Metropolitan Council indicated that the PCE value for heavy truck varies from 2.0 to 4.0.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.