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37 chapter six ConClusions AnD suGGEsTions FoR FuRTHER REsEARCH The review conducted for this synthesis revealed that the development of truck trip generation rates for air cargo facilities has historically received little support or attention from planners, airports, the air cargo industry, or researchers. To the extent that literature related to air cargo facility developÂ ment, planning and operations exists, relatively little of this literature focuses on or addresses air cargo facilityÂrelated truck trip generation rates, likely because most airports maintain a primary focus on passenger traffic rather than freight. As the value, volume, and importance of air cargo grows, airports and transportation planners may place more emphasis on truck traffic associated with that growth. The interviews conducted for this synthesis collectively suggest that there has been only limited interest in understanding the truck trips generated by air cargo facilities, particularly on offÂairport roadways. The information and data required to develop these truck trip rates are not readily available to planners and researchers. For example, the most robust and precise data for air cargo facilities is generally collected and maintained by private air cargo carrier firms, and is considered proprietary and confidential. For the most part, these firms will only share such data on a caseÂbyÂcase basis, as deemed appropriate by corporate officials. However, when these firms do share their data, it is typically aggregated in a manner that allows a user to understand only total tonnages or trucks to and from a facility, sometimes by time of day. The other options for obtaining the data to support development of truck trip generation rates are limited and potentially resourceÂintensive. Several airport officials suggested conducting vehicle counts at access points on air cargo facility roadways and/or surveys of truckers. However, it appears to be uncommon that public agencies outside of airport authorities, such as metropolitan planning organizations, city or county planning and transportation departments, and state departments of transÂ portation, systematically conduct such efforts or collect such data. Again, it is likely that the limited resources available to understand airport ground traffic are allocated mainly to passenger operations. The principal gap in existing practices remains the lack of availability of current and usable data (or data confidentiality requirements) on air cargo facilityÂrelated truck trips. Without data that proÂ vides a fine enough level of granularity to discern and understand the details of truck trips serving air cargo facilities, such as volumes, tonnage, times of day, and types of trucks, it will be difficult to develop guidance that practitioners and airports can apply with confidence. As noted in this report, the approach employed in the 1990 LAX Airport Study may have appliÂ cability to a wider spectrum of airports. Such application would require additional and more robust data to be obtained for the subject airport. The âtrucks per tonâ method was employed for LAX 2010 truck trips using data available through the LAX traffic generation reports and compared the results with actual traffic counts (with some assumptions). This effort produced comparable and reasonable truck trip numbers. However, additional research would help to evaluate this method for other large airports (using actual daily truck trip counts with a truck count survey) and compare with any truck trip modeling results (if done and available for the region/airport) to be able to suggest the most effective approach to use. The only way that different approaches could be evaluated/validated is by using actual truck counts to/from air cargo facilities, an approach that requires that traffic count data be made available through the airport or by performing the potentially expensive roadside truck surveys. Another option for a planning agency to develop truck trip generation rates is to
38 build a special generation model along with the regionâs travel demand model (similar to SCAG HDT). However, such a model will also require truck count data for validation. Appendix A provides a brief checklist of considerations that planners can use to identify posÂ sible information and data sources and options when conducting research into truck trip generaÂ tion associated with air cargo facilities. Appendix B reproduces the guides developed for the three different groups interviewed for this synthesis, as described in chapter one. Appendix C provides details of potential freight movements data sources that could be used for estimating airport truck trips data.