With the expansion of population and economic activity in the country, freight transportation has grown significantly over the last two decades and has become one of the key economic drivers and environmental concerns in California. In California, the freight system is responsible for one-third of the State's economic product and jobs, with freight-dependent industries accounting for over $740 billion in gross domestic product and over 5 million jobs in 2014. Thus, improving the efficiency of California's freight transport system is vital to our State economy and understanding this system is the first key step to identify the actions necessary to make this system sustainable in the future. Proposal: As part of this project, ARB staff is interested to better understand freight mass movement across the major freight corridors in the state. With the truck body classification capability of the state's new Truck Activity Monitoring System (TAMS), researchers have shown that they can identify different types of trucks and trailers (e.g., 40-ft container chassis vs. 53-ft box type trailer) that are utilized within the freight system. This system is even capable of identifying where in the freight supply chain these trucks are operating. For example, a 40-ft container chassis is mostly used to transport freight from ship to truck and then to rail. So it can be considered as a freight mass transported from port to rail-yards/distribution centers, whereas, a box-type trailer might be used for delivery to a freight consignee. If this system can be integrated with data from Weigh in Motion (WIM) sensors located throughout the State, and commodity flow information from the Federal Freight Analysis Framework (FAF), one could potentially measure the freight mass flux in/out of origin/destination zones. Such a system would enable 1) tracking freight mass movement (both spatial and temporal) across the state; 2) connecting truck classifications to economic and commodity information; and 3) better model freight transportation and thus emissions in California. Expected Impact and Benefits: The results from this study can help to develop strategies to reduce emissions from California's trucks for use in the State Implementation Plan, Scoping Plan, Short Lived Climate Pollutant Plan, and Sustainable Freight Action Plan. The information from this study can also be used to calibrate and validate the California statewide freight-forecasting model (CSFFM) and can help inform freight models under development by metropolitan planning organizations (MPOs). Further, this can improve the heavy-duty vehicle inventory in the ARB's EMFAC motor vehicle emissions model and to predict the effectiveness of various emissions control programs.