Office of Operations Freight Management and Operations
Table of Contents

Quick Response Freight Manual II

13.0 Intermodal Considerations in Freight Modeling and Forecasting

13.1 Introduction

To foster a better appreciation of the need for modeling and forecasting of intermodal freight, it is imperative to first gain an understanding of the concept of intermodalism. Intermodalism generally has been defined in somewhat narrower terms by different segments of the freight transportation industry. For example, for the international seaborne shipping industry, intermodalism implies cargo transport in standard shipping containers. However, for the domestic surface-borne trade, intermodalism would pertain to the transport of highway trailers on railroad flat cars. These differences in characterization of intermodal freight transportation call for a broader and comprehensive definition of the concept of intermodalism, in order to capture different aspects of the intermodal freight transportation system in the context of freight modeling and forecasting, and to assist with better freight planning and policy analysis.

The section begins with a brief overview of the types and characteristics of intermodal freight transportation. This is followed by the pertinent discussion on the importance of considering intermodal freight in the freight planning process for the analysis of current and future transportation issues, policies, programs, and initiatives. From the perspective of incorporating intermodal freight into the freight modeling and planning process, a discussion on the extent to which various elements of intermodal freight transportation are captured in existing freight data sources is then presented, which is followed by discussions of the implications of data constraints/limitations on the development of intermodal freight models, as well as innovative approaches to model intermodal freight demand, within the constraints of existing data sources. The section is categorized into the following sections for the discussion of intermodal freight considerations, including drayage, in freight modeling:

  • Types of intermodal freight transportation;
  • Characteristics of intermodal freight transportation; and
  • Intermodal freight data sources.

13.2 Types of Intermodal Freight Transportation

Intermodal freight transportation involves the use of two or more modes of transportation in a closely linked network for the seamless movement of goods. Intermodalism has gained a particularly strong focus in goods movement in recent decades, both from a policy perspective from the public sector, as well as from a business perspective from shippers and carriers, due to the advantages compared to traditional truck or rail freight transportation related to increased operational efficiency, and economies-of-scale.

Intermodal freight transport typically is associated with containerization or in more general terms, the transport of goods involving direct transfer of equipment between modes without any handling of transported goods. For example, containers transferred directly from a containership onto rail cars, or a highway trailer transferred from a truck onto rail cars. This concept of containerization is more of a technical innovation that has transformed intermodalism, but is not entirely synonymous with intermodalism. Intermodalism, in a more broader sense, can be defined as the movement of goods on two or more modes, involving either direct transfer (as in the case of containerized transport), or intermediate storage (for example, shipments involving truck-rail transloading or cross-docking at LTL terminals, wherein there is intermediate storage and handling of goods before modal exchange).

The following sections describe the different types of direct transfer intermodal freight movements, based on the modes involved in the shipment (for international shipments, the modes involved relate to that part of the shipment occurring in the United States):

  • Sea-Truck – Sea-truck intermodal involves the shipment of goods in containers which are transported on trucks to/from seaports from/to their points of O-D for international exports/imports. The containers are directly transferred between oceangoing vessels (containerships) and trucks at marine container terminals.
  • Sea-Rail – Sea-rail intermodal involves the shipment of goods in containers on oceangoing vessels (containerships), which are transported by rail on the surface leg line-haul movement. The modal transfer process for the exchange of containers between containerships and railroad flat cars depends on the location of intermodal rail yards. In the case of on-dock intermodal yards (rail yards located on or adjacent to marine container terminals), there is a direct transfer of goods between containerships and railroad flat cars (without the use of any other mode), while in the case of off-dock intermodal yards, there is an additional leg of the container movement on trucks, which provides the link between the sea and rail modes.
  • Truck-Rail – Truck-rail intermodal involves the shipment of trailers on railroad flat cars, the trailers being transported by trucks between points of O-D and intermodal ramps. This type of intermodal freight transportation also is referred to as Trailer on Flat Car (TOFC) or piggyback.
  • Air-Truck – Air-truck intermodal involves the movement of goods in air freight containers (typically referred to as Unit Load Devices), which are carried on trucks to/from air cargo terminals from/to their points of O-D.
  • Barge-Truck – Barge-truck intermodal involves the movement of goods in containers or trailers on barges that are transported on trucks for the surface leg of the shipment. Roll-on/roll-off barge transport is an example of barge-truck intermodal movement, in which wheeled containers or trailers are transported on barges, which are loaded and unloaded by the means of ramps, without the use of cranes.

In addition to the common forms of direct transfer intermodal movements described above, there are forms of freight movements involving modal exchanges of goods in the supply chain that are associated with cargo handling and/or storage at intermediate facilities. Examples of these intermediate facilities include bulk transfer facilities, LTL cross-docking terminals, and transloading docks at warehouses and distribution centers. Marine terminals also can play the role of bulk transfer facilities in the case of modal transfer of bulk commodities between oceangoing vessels, and unit trains (for example, for coal).

The modes used in the U.S. intermodal freight transportation system typically depend on the market area, which can be broadly categorized into domestic, international (Canada and Mexico), and international (sea-based) trade market areas. The modes involved with these intermodal trade market areas are briefly described below:

  • U.S. Domestic (Intermodal) Trade – This primarily involves truck-rail intermodal (TOFC or piggyback), while a small fraction also occurs on truck-barge intermodal (involving cabotage activity, and/or shipments between mainland U.S. and Hawaii or Puerto Rico).
  • U.S. International (Canada and Mexico) Intermodal Trade – This primarily involves truck-rail intermodal shipments. However, a few instances of cross-border truck-barge intermodal moves have been observed.
  • U.S. International (Sea-Based Intermodal) Trade – This involves the containerized transportation of goods on surface (truck and/or rail) and marine (oceangoing vessels) modes (sea-truck, sea-rail). International sea-based intermodal trade typically involves sea-truck or sea-rail intermodal movements.

13.3 Characteristics of Intermodal Freight Transportation

Some useful characteristics of intermodal freight transport that are useful to understand from a freight modeling perspective are discussed below.

13.3.1 Drayage

Drayage is an essential component of intermodal freight transportation, which is defined as the movement of a container or trailer on a truck between an intermodal terminal (marine or railroad) and a customer’s facility. Drayage movements in intermodal transportation are particularly relevant from a freight modeling perspective, since they are additional truck trips, which need to be accounted for in order to accurately estimate total truck trips on the highway network. It also is important to understand and model time-of-day distributions of drayage trips and how they interact with auto traffic, based on the operations of intermodal terminals. Drayage truck trips also are a major source of emissions around intermodal terminals, which are modeled as a function of the Gross Vehicle Weight (GVW)-based truck classification. These requirements affect the truck classification schemes used in truck models that use the three truck classes based on GVW ratings (heavy heavy-duty trucks, medium heavy-duty trucks, and light heavy-duty trucks). Typically, heavy heavy-duty trucks (HHDT) are used for intermodal drayage, which have different engine emission characteristics compared to light and medium heavy-duty trucks. In addition to the above considerations, market area is an important parameter affecting intermodal drayage truck trips, which is defined as the maximum radial coverage area around the intermodal terminal for which intermodal transportation retains its cost-effectiveness compared to conventional movement of goods. The costs associated with a truck-rail intermodal move, for example, can be divided into two drayage cost components (costs of drayage from point of origin to the intermodal terminal, and from the intermodal terminal to the point of destination), line-haul cost, and terminal handling costs at the two intermodal terminals. For distances exceeding the intermodal market area, the drayage costs relative to the total intermodal transportation cost become too prohibitive for the entire truck-rail intermodal move to be cost-effective.

13.3.2 Equipment

The types of equipment used in intermodal transportation, as well as equipment ownership and lease issues, can have a significant effect on the magnitude and distribution of modal intermodal freight flows in a region. Following is a list of equipment that plays a critical role in the movement of goods in the direct transfer intermodal supply chain:

  • Containers (international oceangoing intermodal trade) and trailers (domestic and international surface intermodal trade).
  • Intermodal Chassis – They are wheeled frames with container locking devices which can be attached to truck tractors for the highway transport of containers.
  • Intermodal Terminal/Yard Equipment – These are equipments used at marine and rail intermodal terminals for the terminal movement, stacking, loading, and unloading of containers/trailers, which include packers (for lifting containers from the bottom), top lifts (for lifting containers from the top), yard/reach stackers (for stacking containers), hostlers (tractors used for moving containers/trailers), and intermodal lifts and cranes for the loading and unloading of containers/trailers.
  • Transportation Equipment – These are the main modal transportation equipments used for the line-haul transport of intermodal freight. These include truck-tractors, railroad flat cars, container and ro/ro barges, and ocean-going containerships.

The ownership and lease issues related to intermodal equipment can impact the distribution of freight flows, as well as empty truck trips in a region, which is important to understand from a modeling perspective. For example, in the case of international intermodal trade, containers typically are owned by ocean carriers, which entails the need for the truck to pickup/return of empty containers from/to marine terminals. In the case of an export move, the trucking company will pick up the empty container from the port, go to the customer’s location for loading, and take the loaded container to the port (in the case of an import move, the trucking company will have to return the empty container, after unloading at the customer’s location, back to the port). The ownership of intermodal chassis determines the location of chassis yards, which in turn impact the distribution of truck trips. Chassis can be owned by the railroads, terminal operators, intermodal chassis providers (independent companies), or intermodal trucking carriers.

13.3.3 Logistics and Operations of Intermodal Terminals

Operational and logistics issues associated with intermodal terminals also have a major effect on intermodal freight traffic in a region. A major operational issue related to intermodal terminals from a modeling perspective is the time-of-day operations of terminals, which have a direct impact on time-of-day activity of drayage truck trips. In the case of large marine terminals, for example, peak-hour drayage trucking activity can coincide with peak-hour auto traffic on major freight corridors and access routes, thereby leading to congestion, as well as adverse safety and environmental impacts (associated with idling and slow moving vehicles). If there are any particular programs initiated by sea ports to encourage shifting of time-of-day activity of drayage trucking, then the associated changes in time-of-day trucking activity as a result of these programs need to be reflected and incorporated into truck models, to accurately predict time-of-day trucking activity in the region. The PierPass off-peak program at the ports of Los Angeles and Long Beach is an example of an initiative to shift time-of-day trucking activity to avoid peak-hour congestion at the ports, as part of which, a Traffic Mitigation Fee (TMF) is assessed for cargo movements through the ports during the peak hours, to encourage off-peak cargo trucking at the ports.

From an intermodal terminal logistics standpoint, an important consideration for modeling, especially pertinent to international intermodal trade, is the amount of intermodal cargo moving through on-dock yards relative to near-dock intermodal rail facilities. This typically is affected by the capacity of on- and near-dock intermodal yards, as well as the logistics of the inherent intermodal supply chain. This has a major impact on intermodal trucking activity associated with the ports, since cargo moving between seaports and near-dock yards are carried by trucks, and these truck trips need to be accounted for in the modeling process. Another intermodal terminal logistics issue that might be relevant in some scenarios is the transloading of cargo between international containers and domestic trailers. For example, an international intermodal import cargo that arrives at the Port of Oakland to be transloaded to a domestic trailer at a transload facility, and then is carried to an off-dock intermodal yard for loading onto railroad flat cars. These logistical issues have an impact on the distribution of truck trips in the region, which are important for consideration in regional truck modeling. Finally, the sheer increase in size of container ships, the largest of which are approaching 15,000 TEUs in capacity, is affecting the logistics of total rail and truck drayage demand at marine ports.

13.3.4 Cargo Handling at Intermediate Facilities

For intermodal freight movements that involve intermediate cargo handling and storage between modal exchanges, the locations and operations of these intermediate cargo handling and storage facilities impact the magnitude and distribution of freight flows in the region. The operations of different kinds of intermediate facilities, and their impacts on modeling issues associated with freight flows moving through these facilities, is discussed in the following sections:

  • Bulk Transfer Facilities – These are intermediate facilities for transloading of liquid or solid bulk commodities, such as petroleum or gravel, between transport modes, typically between truck and rail. Such facilities generally are operated by railroads close to major industrial bulk commodity production facilities for the large scale and cost-effective transport of these goods by rail. From a modeling perspective, the truck trips between the shipper/receiver’s facility and the bulk transfer facility need to be considered in the modeling process.
  • LTL Cross-docking Terminals – In the case of long-haul LTL trucking activity, the LTL cargo may move through LTL cross-docking terminals in a hub and spoke system where intermediate handling of cargo takes place before cross-docking between long- and short-haul distribution trucks. The term cross-docking in LTL trucking activity typically refers to the immediate truck-to-truck transfer of cargo without (or minimal) warehousing/storage. For each long-haul LTL shipment, there are typically many short-haul distribution truck trips for pickup and delivery between the LTL cross-docking terminal and LTL shippers/receivers whose cargo has been consolidated in a single LTL shipment. An LTL shipment typically is represented in terms of the cargo movement between the two LTL terminals. However, from a modeling perspective, the additional short-haul trips associated with LTL pickup and delivery need to be captured in the model. Also, the differences in truck types used for long- and short-haul pickup and delivery operations in LTL trucking need to be accurately reflected in the model.
  • Transloading Docks at Warehouses and Distribution Centers – Warehouses and distribution centers are important freight facilities with significant intermediate cargo handling and storage between modal exchanges. For a typical warehouse, the transloading activity could be associated with truck-truck or truck-rail transfer of cargo. An example of a truck-rail transloading activity at a warehouse is rail carload shipments arriving at a warehouse, which are eventually transloaded to trucks for outbound shipments, after intermediate cargo handling and storage. Truck-truck transloading activity is more common in the case of distribution centers where cargo is delivered to the facility by trucks, which undergoes intermediate handling/storage, and is then transloaded to trucks for outbound distribution. In developing regional truck models, it is important to consider the linkages of commodity flows between modes as they move through warehouses and distribution centers. In many cases, information on only one leg of the shipment might be available (for example, goods moving into or out of a warehouse), but if considered as part of an intermodal (multimodal) movement with intermediate handling/storage, there are additional modal flows associated with that shipment that need to be considered in the modeling process.

13.4 Intermodal Freight Data Sources

The availability of data sources for intermodal freight shipments in the United States, and the extent to which these sources capture the various ramifications and elements of intermodal transportation, has a major impact on the ability to develop robust models to accurately predict intermodal freight flows in the future. Intermodal freight flows are captured in many standard freight data sources. However, none of the data sources provide all the commodity flow linkages associated with intermodal freight movements. Following are some key areas of limitations of standard data sources in capturing intermodal freight movements:

  • The biggest limitation of standard data sources with respect to intermodal freight flows is that they do not capture all the commodity flow linkages associated with intermodal freight movements. For example, some data sources like CFS represent intermodal freight in terms of commodity flows by intermodal from the point of origin (shipper’s location) to the point of destination (receiver’s location). This freight flow representation precludes the ability to determine the intermodal transfer terminal location, which is a critical input from a modeling perspective to determine truck trip distributions. Another limitation with regard to commodity flow linkages is the representation of import container flows moving to off-dock intermodal yards as sea-rail intermodal, without any indication of the intermediate truck move linking the sea and rail modes. Some data sources also provide freight flows associated with each leg of the intermodal move, in terms of the individual mode associated with each leg (for example, truck move from A to B, rail move from B to C, and a truck move from C to D). However, this type of representation can lead to potential errors in the modeling process. For example, the truck move from A to B, which is a short-haul intermodal drayage move, could be treated by the model as a local distribution truck trip, which can lead to errors in truck classification for the shipment, as well as the number of truck trips associated with that shipment (for example, by using inappropriate payload factors).
  • In many cases, data sources might provide commodity flows in terms of tonnages, without any representation of flows in terms of TEU. This creates problems associated with the need to determine which commodities potentially move in containers, estimating the fraction of the tonnages of each commodity that move in containers, as well as estimating the number of container movements based on tonnages (without any representative information on average tons per TEU by commodity group).
  • In the case of intermodal (multimodal) movements involving intermediate cargo handling/storage, especially at LTL cross-docking facilities, data sources typically only provide the long-haul LTL component of the shipment without any information on local LTL pick up and delivery movements by O-D. This lack of information can impact the accuracy of modeling local LTL short-haul pickup and delivery trips, which are critical components of trucking activity, particularly in an urban area. Similarly, data sources also do not capture the linkages of commodity flows moving through the warehouse and distribution center transload supply chain, information on which is important from a modeling perspective to account for secondary trucking activity associated with these facilities.

Given the above limitations, however, the data provided by standard data sources, coupled with data from other secondary sources (such as seaports, rail yards, etc.), and primary freight data collection efforts, can greatly enhance the capabilities for the robust modeling of intermodal freight flows in a region. The following sections present the potential applications of data available from standard data sources, other secondary sources, and primary data collection programs for intermodal freight modeling and forecasting.

13.4.1 Standard Freight Data Sources

The discussion in this section focuses on data available from standard national freight data sources, which include the FAF database developed by the FHWA and the TRANSEARCH database developed by Global Insight. While there may be other local and regional freight data sources (for example, ITMS database for California), which might provide data on intermodal freight flows, that discussion on which is out of scope of this section.

FHWA Freight Analysis Framework (FAF)

A detailed description of the commodity flow data available from the FHWA FAF is available from another section of the QRFM, on freight data sources. This section is, however, limited to the discussion on intermodal freight data elements in FAF. The 2002 O-D database from FAF provides commodity flows for three distinct market areas, which include U.S. domestic (FAFOD_DOM_2002), border crossing with Canada and Mexico (FAFOD_BRD_2002), and international sea and air borne trade (FAFOD_SEA_2002). The modal information in each of these databases pertains to the modes used in the domestic leg of the shipment, within the United States. The following intermodal freight flow components are captured in the FAF O-D databases:

  • Truck-Rail – Includes truck-rail intermodal shipments.
  • Truck-Air – Includes truck-air intermodal shipments. However, these are included as part of total Air shipments.
  • Other Intermodal – Includes sea-truck, sea-rail, and other intermodal combinations (such as truck-barge). However, this group also includes all less than 100 pound shipments by Parcel, U.S. Postal Service, or Courier.

The O-D level of detail in FAF is limited to Metropolitan Statistical Areas (MSA), Consolidated Statistical Areas (CSA), and balances of states, which are regions encompassing groups of counties. This aggregate O-D detail is a potential limitation when analyzing intermodal freight flows using FAF. However, innovative O-D freight flow disaggregation techniques combined with the modal information from FAF for intermodal flows can find useful applications in intermodal freight flow modeling.

The domestic and border crossing commodity O-D databases from FAF can be used to analyze primarily truck-rail intermodal flows. The origins and destinations in the domestic and border crossing database correspond to final production and attraction locations but not the intermediate intermodal terminal transfer location for truck-rail intermodal flows. From a regional truck modeling perspective, the primary objective of the commodity flow analysis would be to determine the magnitude and distribution of intermodal freight flows between points of O-D and intermodal terminal locations. Since FAF also provides commodity information for truck-rail intermodal flows in terms of tonnages, these flows can be allocated to further disaggregate zones of origin and destination based on corresponding zonal industry employment data, and input-output modeling approaches. The next step would be to determine what fraction of these intermodal freight flow origins and destinations are associated with the various intermodal yards in the region, which can be estimated using an approximate procedure, based on the relative amount of intermodal traffic using various yards. If more detailed information is available from intermodal yards on major origins and destinations of drayage truck trips, this information can be a critical input for the drayage truck trip distribution estimation process.

In the case of the seaborne O-D database from FAF, there are two primary components of international intermodal freight flows that are critical from a modeling perspective. These include drayage truck trips between seaports and customer facilities (mainly warehouse and distribution centers), and drayage truck trips between seaports and near and off-dock intermodal terminal locations. Information on drayage truck trips at seaports can be derived from the “Other Intermodal” modal specification in the FAF database (flows through specific seaports are provided in FAF in the “Port” data field). However, since this mode also includes shipments less than 100 pounds by Parcel, U.S. Postal Service and to Courier, the first step would be to look at the commodity classification for these flows, and exclude all the flows associated with postal, parcel, and courier shipments. The remainder of the intermodal flows will primarily be associated with either sea-truck or sea-rail intermodal flows. The flow fractions associated with each of these intermodal combinations can be estimated based on the analysis of the O-D of shipments.

Most of the long-haul intermodal shipments (greater than 250 miles) can be assumed to occur by sea-rail intermodal, while the short-haul intermodal shipments will primarily be sea-truck intermodal shipments, with trucks providing intermodal drayage between the seaports and customer facilities. The disaggregation of these drayage flows to more detailed O-D locations than MSA/CSA level in FAF might not be a straightforward process since a large fraction of these truck trips might potentially originate/terminate at warehouse/distribution center locations (zonal industrial employment or input-output data cannot be used for the disaggregation process). For sea-rail intermodal shipments, an additional analysis step will be required to determine the fraction of flows through on- and off-dock intermodal yards. The truck trips associated with the flows through off-dock yards will then need to be allocated to zones containing off-dock rail terminal facilities. The analysis steps associated with both the sea-truck and the sea-rail intermodal flows from FAF will need to be potentially supplemented with data from the Ports as well as primary data collection around Port facilities. For example, ports can provide data on the fraction of rail intermodal flows through on- and off-dock yards, while roadside intercept surveys of trucks conducted at marine container terminal gate locations can be used to estimate O-D distribution of drayage truck trips, as well as O-D facility types used by drayage trucks.

Since FAF provides forecast O-D commodity flows (the 2002 O-D commodity flow database includes forecasts every five years from 2010 to 2035, while the 2007 benchmark O-D database will include forecasts through 2040), the intermodal commodity flow data from FAF offer the capabilities to develop intermodal freight flow forecasts when used as inputs to intermodal freight models.

13.4.2 TRANSEARCH

Detailed discussion on the freight data elements in TRANSEARCH are provided in the freight data sources section of the QRFM. This section is limited to the discussion on intermodal freight flows in TRANSEARCH. TRANSEARCH is a proprietary database developed by Global Insight, and is one of the most comprehensive data sources of domestic and international freight flows in the United States. One of the primary strong points of the TRANSEARCH database is the provision of commodity flows at the county level of detail, which increases its utility for applications in the analysis of freight flows at detailed regional levels.

TRANSEARCH is unique compared to other freight data sources in the treatment and representation of intermodal freight flows. TRANSEARCH represents intermodal freight flows in terms of separate O-D flows for each leg of the intermodal movement. For a truck-rail intermodal move, for example, there are three components of O-D flows, which include the truck drayage portion of the flow from the point of origin to the intermodal terminal, the rail shipment from one intermodal terminal to the other, and the truck drayage flow from the intermodal terminal to the point of destination. TRANSEARCH estimates the rail portion of rail/truck intermodal activity primarily from the STB Waybill sample, which is supplemented with data collected directly from the railroads. In addition, information directly obtained from leading intermodal marketing companies and drayage carriers is used to estimate the truck drayage portion of truck-rail intermodal flows. In order to separate the truck drayage trips from other short-haul truck trips, the drayage portion of the intermodal movement is indicated by the STCC commodity code 5020, which stands for intermodal truck drayage. However, due to the use of this classification, the type of commodity moving in the drayage truck trip remains unknown.

The separation of truck and rail portions of truck-rail intermodal flows in TRANSEARCH, and the denotation of truck drayage flows with unique codes, makes TRANSEARCH particularly robust for applications in intermodal freight flow modeling. However, there might be some issues that might need to be addressed when using TRANSEARCH for addressing intermodalism in regional freight models. Although TRANSEARCH accounts for truck and rail modes of truck-rail intermodal separately in the database, there is no way to determine the commodity flow linkages for these intermodal flows, from the point of origin to the point of final destination of the shipment. This is because the rail portion of the intermodal shipment is incorporated into the total rail flows in tons for O-D pairs (the origin and destination for rail intermodal being the locations of the intermodal terminals for the origin and destination of the rail shipment), which precludes the ability to extract the fraction of the total rail tonnages from a particular origin to destination by rail intermodal, compared to rail carload. The consequences of this from a modeling perspective is that for a truck drayage move in TRANSEARCH, particularly intracounty drayage moves, it might be difficult to determine whether it is a drayage move from a shipper’s location to an intermodal terminal (as part of the first leg of the intermodal move), or from an intermodal terminal to the receiver’s location (as part of the last leg of the intermodal move). In these cases, an approximate procedure can be used to determine the fractions that are first leg versus last leg drayage moves, by looking at the inbound and outbound rail tonnages for that county.

13.4.3 Additional Sources of Intermodal Freight Data for Modeling Applications

The following are some additional sources of intermodal freight flow data that can find potential applications in the development of models incorporating intermodal freight flows:

  • Seaport Data – Seaports typically collect and maintain data on many different elements related to international intermodal trade (particularly because of its rapid growth rate) for infrastructure planning, and economic and environmental impact analyses. Some of these data elements that can serve as potential inputs to intermodal freight models include the following:
    • Fraction of international container traffic moving through on- and off-dock intermodal yards, which is a critical input to determine truck trips performing drayage to/from off-dock intermodal yards.
    • Port forecasts of intermodal container traffic in TEUs, which can be used to estimate future port truck trip generations (productions and attractions).
    • Truck drayage activity around marine container terminals by time of day. This can be used to develop time-of-day models, as well as for overall validation of port truck models.
    • Bulk transloading activity in and around Port facilities, by type of commodity. This information can be useful to account for the flows through ports that move by multiple modes, but are associated with intermediate handling and storage.
  • Primary Data Collection Programs – A separate section of the QRFM discusses in detail the applications of primary freight data collection programs for freight modeling and forecasting. Some potential applications of primary freight data collection programs for direct transfer and intermediate handling/storage intermodal freight modeling are presented below:
    • Gate intercept surveys conducted at marine container terminal gate locations can provide useful information on the O-D distributions of drayage truck trips, as well as the types of freight facilities that drayage truck trips originate from or are destined to. Information on the origin or destination facility type of drayage trips is useful from a modeling perspective, because locations such as warehouses, distribution centers, and other facilities (i.e., container freight stations and LCL consolidation/deconsolidation terminals) generate secondary truck trips as part of the overall intermodal supply chain, which need to be accounted for in regional truck models. Roadside intercept surveys also can inform the locations of off-dock intermodal yards used by drayage truck trips for the distribution of drayage flows to off-dock yards.
    • Vehicle classification counts around marine container and rail intermodal terminals are critical inputs for developing trip generation models, as well as for model validation.
    • Trip diary surveys of intermodal drayage trucks can provide useful information to understand and model trip chaining activity. For example, an entire drayage truck trip chain starting from the trucking terminal location and ending back at the terminal location can be tracked in a trip diary survey. There could be different combinations of trip chains associated with such a drayage move, involving variations in where the empty container is picked up and dropped off, whether the truck has the chassis when originating from the terminal location or has to pick up the chassis from a separate location (like a chassis yard), etc. which are critical pieces of information that can significantly improve the modeling of intermodal truck trips in a region.
    • Establishment surveys of terminal locations, for example, LTL cross-docking facilities can provide information on the types of trucks used for long-haul versus local LTL pickup and delivery operations, time-of-day operations of LTL trips, and major origin and destination locations of LTL pickup/delivery trips, which can serve as useful inputs for the modeling of truck trips associated with LTL cross-docking terminals.

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