Representing Freight in Air Quality and Greenhouse Gas Models (2010) / Chapter Skim
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Pages 116-140
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From page 116... ...
The Conceptual Model is based on a "link and node" transportation network. The link and node framework is the basis for representing roadway networks in travel demand models, and it is also regularly applied to other modes (e.g., rail)
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From page 117... ...
Strategy planning creates a high-level overview of the information needs of the stakeholders and the system functional areas that will fulfill such needs. In this case, this entails a closer look at the information needs of the four main categories of stakeholders (private industry, transportation agencies, environmental regulatory agencies, and environmental organizations)
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From page 118... ...
The models also estimate external trips. In the second step, trip distribution, the model combines internal and external truck trips by truck type onto an origin-destination matrix.
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From page 119... ...
(190) Instead of using modal activity and emission factors, GIFT models a supply chain as a collection of links and nodes, in which each link represents a trip by specific mode, and each node represents freight handling locations, including railyards, intermodal centers, and warehouses.
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From page 120... ...
, so they can develop leaner and more cost-effective supply chains while promoting environmental stewardship. Private firms will use the model to understand how choices in terms of supply chain design, facility location, mode choice, route choice, inventory levels, packaging, and delivery patterns affect the environmental performance of their supply chains.
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From page 121... ...
These groups 121 Private Industry (shippers/carriers) Evaluate environmental performance of supply chains Environmental Regulatory Agencies (EPA/ARB)
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From page 122... ...
; • Compare environmental performance of different corridors in order to understand the correlations between corridor capacity, commodity mix, mode share, and environmental performance; 122 Type of Analysis Objective Modes Audience Global/National Calculate freight emissions inventories associated with large geographic areas. All Environmental Regulatory Agencies Freight Corridor Calculate freight emissions associated with a specific corridor.
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From page 123... ...
Input parameters to determine freight activity will differ by mode. Trucking activity likely will come from travel demand models, and it is important to understand how such estimates are determined.
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From page 124... ...
Ground support equipment used to service air cargo also needs to be accounted for -- this would include information on the hours of use, duty cycle, and fuel type. Outputs from this application include freight emissions associated with different scenarios characterized by traffic throughput, operational characteristics (e.g., idling times)
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From page 125... ...
This type of application will be most useful to shippers, carriers, or logistics providers interested in evaluating the environmental performance of their supply chains, and in understanding the effects of mode, route, and equipment choice on emissions. Input parameters will include supply chain design, facility location, mode choice, route choice, inventory levels, packaging, delivery patterns, and equipment characteristics.
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From page 126... ...
For example, the analysis of freight emissions in a metropolitan area is to likely rely on travel demand models to estimate truck activity on a local transportation network. In this case, mode choice and route choice will already be determined.
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From page 127... ...
For example, for those analyses that rely on travel demand models to estimate truck activity over specific links, all processes under the planning of transportation service 127 • Supply chain design • Link characterization • Node characterization 1. Transportation Network Design • Determination of commodity flows • Determination of service level • Mode choice • Route choice 2.
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From page 128... ...
Activity Profile PRO Activity profiles represent driving cycles, duty cycles, or any other distribution of vehicle activities that has an effect on emission factors. Area ARE Combination of links and nodes.
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From page 129... ...
There is a mutual dependency between supply chain design and other processes. Both mode choice and route choice depend on an initial selection of logistics facilities, while the selection of transportation-related facilities depends on mode and route selection.
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From page 130... ...
Truck Estimate congestion and average speed Average speed Measured in miles per hour, average speed either can be an input parameter as in the case of travel demand models, or it can be estimated based on link capacity and traffic volumes. Truck Estimate emission factor Congestion Road level of service, varying from A to F
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From page 131... ...
Ocean-Going Vessels Calls, ship type, engine type, engine model year, propulsion and auxiliary engine power, ship size (DWT or TEUs) , fuel type Harbor Craft Population by engine type, number of engines per vessel, engine power by type, deterioration factor, growth factor, engine age, median life, scrappage, use of retrofit devices, fuel type Cargo Handling Equipment Population, engine power, deterioration factor, growth factor, engine age, median life, scrappage, use of retrofit devices, fuel type Air Freight Engine type, fuel type, fraction of payload used for air cargo, aircraft type, fuel flow rates, aircraft performance (throttle setting)
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From page 132... ...
Exhibit 4-11 provides examples of activity metrics specific to each mode of transportation. 132 Mode Activity Metrics Activity Profile Parameters Heavy-Duty Trucks VMT, idling time, ton-miles Driving cycle, level of service, average speed, bin allocation Rail Train-miles, car miles, idling time, ton-miles Duty cycle Ocean-Going Vessels Calls, propulsion power Load factors, vessel speed Harbor Craft Annual activity, fuel consumption Load factors by engine type, duty cycle Cargo Handling Equipment Load factor, activity Emission factor, duty cycle Air Freight TIM (cruise, approach, taxi/idle, takeoff, climb out)
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From page 133... ...
Source of emission factors by mode. Mode Source of Emission Factors Heavy-Duty Trucks MOVES, Mobile6 Rail EPA guidance Ocean-Going Vessels EPA guidance Harbor Craft ARB NONROAD or EPA OFFROAD models, other EPA guidance, other studies Cargo Handling Equipment ARB NONROAD or EPA OFFROAD models, other EPA guidance Air Freight ICAO emissions certification databank and fuel flow rates
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From page 134... ...
. Depending on data availability and the complexity of analytical methods, emissions might be calculated separately by vehicle type or other factors that affect emission factors (e.g., average speed, road level of service)
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From page 135... ...
For example, users can create different scenarios to test the effects of changes in the level of network aggregation, freight demand, service levels, mode choice, route choice, and equipment configuration. The effects of emission reduction strategies also are captured by the Conceptual Model, including the strategies affecting emission factors, freight activity, fuel efficiency, and congestion.
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From page 136... ...
. All of the subsequent processes are necessary, including equipment configuration, 136 Facility Type Global/National Corridor Metropolitan Facility SupplyChain Supply Chain Design Link Characterization Node Characterization Determination of Commodity Flows Determination of Service Level Mode Choice Route Choice Equipment Configuration Determination of Loading Patterns Determination of Freight Activity Calculation of Fuel Consumption Determination of Emission Factors Calculation of Emissions Spatial Allocation of Emissions Temporal Allocation of Emissions Analysis of Scenarios Uncertainty Analysis Mandatory Applicable Not Applicable Key: indicates that a parameter is analyzed in the way denoted by the column: indicates that the parameter is not discussed in the way denoted by the column.
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From page 137... ...
Because vehicle activity is provided as an external input parameter, the processes regarding commodity flows, service level, mode choice, route choice, and loading patterns are not relevant to this application. As in other applications, the subsequent processes are required, including equipment configuration, freight activity, and emission factors, as is the calculation of fuel consumption (if emissions are calculated from fuel consumption)
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From page 138... ...
Input parameters include facility location, shipment characteristics, mode choice, route choice, inventory levels, packaging, delivery patterns, equipment characteristics, and timeframe. Outputs from this analysis include freight emissions associated with the transportation necessary to manufacture and distribute product X under different scenarios in each of the three supply chains.
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From page 139... ...
. Truck and rail routes can be subdivided into multiple links, if detailed information about capacity, grade, average speed, and congestion level are available.
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From page 140... ...
For example, different emission factors will be determined for different ship types for the following operational modes: cruise, reduced speed zone, maneuver, and hotelling. Calculation of Emissions As previously indicated, freight emissions are generally the product of freight activity (e.g., fuel consumed, energy generated, or VMT)
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