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58 CHAPTER 5 Conclusions and Recommendations The literature review found that there is a considerable body mode-choice parameters. Sufficient data were available of research associated with developing new methods for ana- from a variety of sources that could provide information lyzing the transportation issues associated with freight. Those about possible decision variables affecting mode choice. The methods are suitable for addressing a variety of topics of con- analysis showed that distance was the primary determinant cern to public decisionmakers. Those models can be classified of mode choice for most commodities, and that other deci- according to a framework and that classification can be applied sion variables were only significant when used in a function to those models used by both the public and private sectors. together with distance. The inability to develop better mod- The most well-developed applications in support of public els of freight mode choice suggests that those modal deci- sector decisions were time series and commodity-based mod- sions are due to localized logistics and business decisions els, with a growing interest in, and application of, network and that might not be easy to forecast. The inability to define bet- microsimulation models. A survey of staff supporting public ter mode-choice functions suggests that methods that pivot sector decisionmakers found a general satisfaction with the from observed mode shares might be more appropriate. types of models that are available, but a general concern about the availability and quality of data that can support public The literature review, survey, and research led to the devel- decisionmaking for freight policies, programs, and projects. opment of a proposed guidebook for freight forecasting. The The research topics pursued focus on the use of publicly avail- proposed 10-step process should provide suitable guidance able or low-cost data that can support the improvement of the for transportation planners to include freight flows, and flows models used in freight forecasting and analysis. of commercial trucks serving purposes other than carrying freight, into their forecasting process. Research into the use of low-cost GPS data for trucks, Section 3.2 of this report discusses topics that, although not as available, from subscribers to commercial monitoring chosen for additional research in this project, were identified services, found that these data can be easily processed to as areas that might fill critical gaps in the freight forecasting improve the understanding of where trucks stop, and to processes. Additionally, the research topics that were addressed identify the connections between those truck stops. Both suggested the following additional avenues for research: the interchange of trips between land uses and the average characteristics by trip were found to be similar among four The GPS research topic suggests that the utilization of observed metropolitan areas. commercial subscription GPS data, especially as these data Research in the use of publicly available truck classification are improved through the addition of more explanatory data together with publicly available commodity flow data, variables such as engine status or vehicle type, is especially as assigned to a highway network, found that flows by dif- promising. ferent commodities were fairly similar both seasonally The seasonal and temporal flow research topic suggests that within a year and temporally within a day. This seasonal additional emphasis on obtaining complete continuous finding was compared with economic trade data from the truck classification count data for entire years, and the uti- economic census of manufacturers. The comparison showed lization of that data to develop suitable factors, is warranted. that economic activity by commodity/industry, which would The research in the use of commodity flow databases as an be expected to result in freight flows, was also generally RP survey topic suggests that the utilization of flow data for uniform throughout the year. historical years, as well as potential decision variables for Research in the use of publicly available commodity flow these same years, could lead to promising insights about data found it to be suitable for use as an RP survey to develop how mode-choice decisions are made.