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57 technology or fuel, nor would freight policies be expected to the length of trips in the chain, and the degree to which the change these elements. However, the steps described above next stop is governed by the characteristics of the current stop. directly consider the changes in demand and operations, as Section 3.3 described research that was conducted using measured by speeds and times. inexpensive GPS data to determine this information. The Benefits and impacts are calculated based on using the records of trucks subscribing to GPS services were examined demand and operational performance associated with freight and processed in several metropolitan areas. Values were pro- projects, programs, and policies. The outputs of these evalu- duced that can be used in truck chaining models. Truck GPS ations may be monetized, may be in environmental emis- subscription records can be expected to become more com- sions, or in other units that may allow for useful comparisons. monly available. Ways to disclose more detailed information The benefits models may be simple spreadsheet formulations about the type of truck without disclosing proprietary infor- or complicated evaluation packages such as FHWA's IDAS or mation are likely to be developed. This may preclude the need STEAM software programs. The interaction with the freight for expensive and time-consuming survey efforts and may forecasts is to process the outputs of freight forecasting into a make truck freight chaining models more widely available. format that can be used as inputs into these evaluation mod- In addition to truck activity chaining in freight, the partner- els. This may require geographic or temporal aggregations of ship between public and private freight interests is likely to the outputs for the freight forecasting process. The output of require improved models for the total logistics process. These this step is typically used in proving the values for the per- models are necessary for the public and private decisionmak- formance measures that were previously described in Step 2. ers to have adequate information to determine the value of publicprivate partnerships. Similarly, some network and facility design models sup- 4.2 New Methods to Generate porting freight, which are primarily used to support private Freight Demand and investment decisions, may need to be available in public forms Performance if decisions on the value of publicprivate partnerships to Although the freight forecasting process described in the develop these facilities are to be considered. steps above can adequately support most existing public deci- The outreach to public decisionmakers identified the lack of sions, it is not clear that they will always be able to provide this data as a serious gap in preparing freight forecasts. Improve- support as the decisions under consideration change. New ments in freight data collection were not a focus of this project methods of monitoring, regulating, and charging for vehicle because this is being pursued by TRB and U.S. DOT as well as operations may require different models. For passenger activ- other agencies in many on-going research projects. However, ities, this has led to the development of activity-based model- the data that currently are available may be better utilized to ing, where trips are not considered in isolation but are consid- prepare the necessary freight-related data. The research topics ered as a chain of trips supporting those activities. A variety of investigated in Section 3 were specifically chosen to exploit research is underway to study how freight and truck activities existing public, available--or in the case of subscription GPS-- would function as activity/chaining models. In order to sup- low-cost data. That research has shown that, in addition to new port these activities for truck and freight models, additional and improved data collection activities, efforts to better use research is needed to determine the number of trips in a chain, existing data could help fill freight data gaps.