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Cargo Surveys 143 craft and availability of belly hold capacity in the market. For this reason, air cargo is often con- solidated over a wide geographic area and trucked to a gateway or major hub airport where ade- quate capacity exists to fly the cargo to its destination. Air cargo data are collected and are available at an aggregate level from federal statistics agencies as a reporting requirement under various regulations. These data are available as total tonnages for inbound and outbound cargo. In the case of international trade, there may be additional data avail- able on tonnages of air cargo by commodity. In the preparation of any cargo study, these sources should be explored thoroughly as a prelim- inary source of data. However, given the purpose of air cargo studies, this aggregate level of data is frequently inadequate. Additional characteristic data are required, including the following: Weight and/or volume. Ultimate origin and destination. Times at origin and destination. Commodity type or value. Flight information. Truck trip characteristics. Basically, this is the information available on an air cargo waybill. This information is, naturally, highly valued by the shippers and forwarders, guarded by privacy rules, and not released easily. A concerted effort is required to obtain even a small sample of data for a single highly focused study. It may, however, be possible to obtain information at a summary level. While the best data for an air cargo study may not be available, there are many other sources that should be investigated before taking on the expense of a survey. As mentioned, some air cargo data are available through regulatory reporting requirements. Another source of data might be munic- ipal and state agencies that conduct truck surveys and interviews. For basic truck volumes in and out of airport cargo facilities, the local municipality may have traffic count information, which can be used to estimate both the volume of activity and patterns over the counting period. With the advent of Intelligent Transportation Systems, there are an increasing number of auto- mated truck pseudo-tracking systems. The I-75/AVION is one such system. It allows selected transponder-equipped trucks to be cleared electronically at weight and inspection stations, while allowing all participating U.S. states and the Province of Ontario to maintain existing regulatory regimes. The weight and inspection stations are equipped with automatic vehicle identification (AVI) and automated weigh-in-motion (WIM) scales. Such systems are based on intelligent tags that track the truck and, by extension, its contents along a corridor. Exploring such data sources may provide information related to air cargo activity. When all these sources of data have been investigated and the available information is still insuf- ficient for the planned analysis, then consideration should be given to collecting additional data through a survey. 10.3 Survey Methods Planning an air cargo survey is not a simple matter of planning a routine survey. There is little experience to draw upon, and therefore virtually no standard practices that can be applied, or mod- ified, for a particular airport. Any survey designed to capture air cargo data is likely breaking new ground. To date, the most common survey method for air cargo is similar to stakeholder interviews. Although shippers and forwarders may be reluctant to release detailed information on air cargo