SMOKE provides two ways of processing mobile sources using MOVES. (Recall that by “mobile sources” in SMOKE we mean on-road mobile sources.) The first approach is to compute mobile emissions values prior to running SMOKE and provide them to SMOKE as input; we call this the precomputed-emissions approach. The second approach is to provide SMOKE with VMT data, Vehicle population (VPOP) data, meteorology data, and MOVES outputs, and have SMOKE compute the mobile emissions based on these data; this is called the MOVES approach. These approaches are not mutually exclusive, so it is possible to provide both precomputed emissions and VMT and VPOP data to SMOKE and have the system compute only some of the emissions using MOVES outputs. Both processing approaches can produce criteria, particulate, and toxics emissions results.
The precomputed-emissions approach is quite similar to the processing method for area sources. In fact, Figure 2.8, “Base case area-source processing steps”, Figure 2.9, “Future- or past-year growth and optional control area-processing steps”, and Figure 2.10, “Alternative future- or past-year growth and control area-processing steps” from Section 2.8.2, “Area-source processing” show exactly the processing steps needed for processing mobile sources using SMOKE and the precomputed-emissions approach. As in base-case processing for area sources, emissions in the inventory file are subdivided to hourly emissions during temporal allocation, assigned chemical speciation factors during speciation, and assigned spatial allocation factors during gridding. The merge step combines the hourly emissions, speciation matrix, and gridding matrix to create model-ready emissions. For future- or past-year processing, the growth and controls step is added to create the growth and control matrices, while the grow inventory step converts the inventory from the base year to a future or past year. The control matrix can be optionally used in the merge step to apply control factors to the future- or past-year emissions. Note that, unlike the VMT approach, in the precomputed-emissions approach SMOKE will not model the variations in emissions caused by temperature, humidity, or other meteorological settings.
The MOVES approach is much different from the precomputed-emissions approach. Figure 2.13, “MOVES mobile RatePerDistance processing steps” and Figure 2.14, “MOVES mobile RatePerVehicle and RatPerProfile (off-network) processing steps” summarize the MOVES approach. First, county total VMT data by road class and vehicle type or county total VPOP by vehicle type are input to SMOKE. The chemical speciation step computes the chemical speciation factors for each county, road class, vehicle type, emissions process (e.g., exhaust start, exhaust running, evaporative processes, extended idle, and crankcase), and pollutant and stores the necessary factors for this transformation. The gridding step allocates the sources to grid cells and uses spatial surrogates to allocate county-total emissions to grid cells, storing the factors needed for these allocations.
The approach for running MOVES for SMOKE relies on the concept of reference counties and fuel months. The concept of reference county refers to running MOVES for a single county, which is the reference county, to represent itself and other counties that share the same MOVES input parameters and thus have the same emission rates for any given speed, temperature and humidity. A reference fuel month similarly refers to a reference fuel month's MOVES run that contains the temperatures that occur in neighboring months as well as the representative month. The mapping of calendar months to a representative month should be assigned on the basis of shared fuel parameters, because it is the interaction of fuel and temperature that is important. For example, an average-hourly temperature of 70°F may occur in some hour of any day in each of four months: May, June, July and August. If those four months share the same fuel properties (i.e. summer fuel) then an emission factor will be determined for just the representative month, reducing by a factor of four the number of calculations that MOVES needs to perform.
Unlike MOBILE6, MOVES differentiates between on-roadway emission processes and off-network emission processes. Figure 2.13, “MOVES mobile RatePerDistance processing steps” summarizes the approach used by MOVES for on-roadway mobile sources. The on-roadway emission process includes county-total VMT and average speed inventory as input. The off-network emission processes use the county-total vehicle population by vehicle type as input. Figure 2.14, “MOVES mobile RatePerVehicle and RatPerProfile (off-network) processing steps” summarizes the approach used by MOVES for off-network mobile sources. Both on-roadway and off-network emission processes do require real gridded meteorology data from MCIP files to estimate temperature-dependent emission rates.
In sections later in this chapter, we describe the SMOKE programs that are needed for each of the processing steps just described for MOVES processed mobile sources, and additional details about what activities are accomplished during each step. These sections are:
Processing mobile sources involves a number of concepts that are unique to mobile sources. These include a special classification of road types in MOVES, SMOKE and MOVES vehicle types, emissions processes, MOVES emission factors, reference counties, reference fuel months, and meteorological processing using Met4moves. The following subsections and sections 2.16 and 2.19 explain these topics in more detail.
MOVES can model five different road types: rural restricted/unrestricted access, urban restricted/unrestricted access, and off-network (used for emission processes that are not road dependent, such as exhaust start, extended idle, and crankcase). Table 2.2, “Road class and corresponding MOVES road type” indicates how the 13 SCC road classes are mapped to the five MOVES road types. The fractions for disaggregation are applied at the county level and can be found in the sccroadtypedistribution table in the MOVES model.
Table 2.2. Road class and corresponding MOVES road type
|SCC Code||SCCRoadTypeID||MOVES roadTypeID|
|110||Rural Interstate||Rural Restricted Access|
|130||Rural Principal Arterial||Rural Unrestricted Access|
|150||Rural Minor Arterial||Rural Unrestricted Access|
|170||Rural Major Collector||Rural Unrestricted Access|
|190||Rural Minor Collector||Rural Unrestricted Access|
|210||Rural Local||Rural Unrestricted Access|
|230||Urban Interstate||Urban Restricted Access|
|250||Urban Freeway||Urban Restricted Access|
|270||Urban Principal Arterial||Urban Unrestricted Access|
|290||Urban Minor Arterial||Urban Unrestricted Access|
|310||Urban Collector||Urban Unrestricted Access|
|330||Urban Local||Urban Unrestricted Access|
Note that SMOKE assumes that a portion of the VMT data supplied for interstates and freeways are attributable to freeway ramps. Therefore, SMOKE computes a composite emission factor from the freeway and freeway ramp emission factors from MOVES and maps the composite to the interstates and freeways.
The vehicle types used in SMOKE’s on-road mobile source processing are described in Table 2.3, “Vehicle type codes and descriptions”. The codes (e.g., 0100) should be used in the cross-reference files.
Table 2.3. Vehicle type codes and descriptions
|0100||LDGV||Light Duty Gasoline Vehicles|
|0102||LDGT1||Light Duty Gasoline Trucks 1|
|0104||LDGT2||Light Duty Gasoline Trucks 2|
|0107||HDGV||Heavy Duty Gasoline Vehicles|
|3000||LDDV||Light Duty Diesel Vehicles|
|3006||LDDT||Light Duty Diesel Trucks|
|3007||HDDV||Heavy Duty Diesel Vehicles|
MOVES can produce emission factors for possible combinations between 13 MOVES vehicle types (sourceTypeID) and fuel types (fuelTypeID). For SMOKE to assign these emission factors to the mobile sources, the emission factors must be aggregated to the 8 vehicle types (SCCvtypeID) listed in Table 2.3, “Vehicle type codes and descriptions”. To perform this aggregation, MOVES disaggregates emission rate output into the 31 vehicle model years. Fractions that map MOVES sourceTypeID by model year and fuleTypeID to SCCVtypeID to SCCVtypeID are found in the sccvtypedistribution table of MOVES.
Once the applicable SCC is determined by SCCvtypeID and SCCRoadTypeID, MOVES aggregates those emission rates by SCC over vehicle model years using travel fraction. Travel fractions are simply weighting factors that sum to 1 over all model years; they are used to aggregate emission rates over model years to produce a single SCC-wide emission rate instead of a rate for each of the 31 vehicle model years. Travel fractions are based on mileage accumulation by vehicle model year and/or age distribution by model year.
SMOKE handles SCCs differently for on-road mobile sources compared with all other source categories. SMOKE programs assume that on-road mobile SCCs have the following form:
The Smkinven program populates SMOKE’s internal fields for vehicle type (vehicle code) and road type by extracting them from the SCC and
converting the 3-digit road class to the 2-digit road type (using the mapping provided in the
MCODES file). During cross-referencing for any mobile-source processing step, SMOKE builds internal SCCs of the form:
These internal SCCs are created by SMOKE for both the inventory file and the cross-reference file. Therefore, any information included in the unused “X” portion of the inventory SCC will be ignored during the cross-referencing. If you refer to the on-road mobile cross-referencing hierarchies provided with each program that uses cross-referencing in Chapter 6, SMOKE Core Programs, the vehicle type and road type are a part of the hierarchy, but the inventory SCC code is not. The internal SCCs are used so that the correct hierarchy can be used (in which the vehicle type is a more specific descriptor). See Section 2.3.5, “Source Classification Codes” for a description of the “left to right” hierarchy of the parts of an SCC.
In some cases, SMOKE errors and warnings that appear when processing on-road mobile sources will contain the internal SCC instead of the source’s inventory SCC. The information provided in this section can help you determine which source is actually a concern.
Although the “X” portion of the inventory SCC is not used as part of the cross-referencing assignments in SMOKE, it is important that any SCC that appears in the cross-reference file also appear in the inventory in exactly the same way. This is because SMOKE filters the cross-reference files before using them by comparing the SCC in the cross-reference file to the complete list of SCCs in the inventory. This comparison considers the “X” portion of the SCC, and if the SCC that you want to use is in the cross-reference with a different “X” than what is in the inventory, the cross-reference record will be dropped and will not be applied to the sources.
The approach for running MOVES for SMOKE relies on the concept of reference counties. These are counties that are used during the creation and use of emission rates to represent a set of similar counties (i.e., inventory counties) called a county group. The purpose of the reference county approach is to reduce the computational burden of running MOVES on every county in your modeling domain. By using a represenative county, the user generates key emission rates for the single county in MOVES and then utilizes these factors to estimate emissions for all counties in the county group through SMOKE. The reference county is modeled at a range of speeds and temperatures to produce emission rate lookup tables (grams/mile or grams/vehicle/hour, depending on mobile emission process). The variables that are assumed to be constant across the county group members (and the reference county) are fuel parameters, fleet age distribution and inspection/maintenance (I/M) programs. The variables that can vary within the county group are vehicle miles traveled (VMT), source type vehicle population, roadway speed, and grid cell temperatures. Determining the reference counties and their respective county groups is a key aspect of utilizing the SMOKE-MOVES tool. It is ideal for the user to create each county group based on the similarity between the county characteristics (e.g., urban and rural) and the meteorological conditions (e.g., temperature and relative humidity). The user should avoid grouping counties that have significantly different meteorological conditions.
Along with the concept of reference county approach, the concept of a fuel month is very important. It is used to indicate when a particular set of fuel properties should be used in a MOVES simulation. Similar to the reference county, the fuel month reduces the computational time of MOVES by using a single month to represent a set of months. To determine the fuel month and which months it corresponds to, the user should review the State-provided fuel supply data in the MOVES database for each reference county. If the fuel supply data change throughout the year, then group the months by fuel parameters. For example, if the grams/mile exhaust emission rates in January are identical to February's rates for a given reference county, then use a single fuel month to represent January and February. In other words, only one of the months needs to be modeled through MOVES.
The meteorological data processor program Met4moves prepares spatially and temporally averaged temperatures and relative humidity data to set up the meteorological input conditions for MOVES and SMOKE using the Meteorology-Chemistry Interface Processor (MCIP) output files.
Met4moves must be run after MCIP and before the MOVES driver script “Runspec_generator.pl” and Smkinven.
The following are the major processing steps that Met4moves performs:
Read the reference county cross-reference file
MCXREF that contains a list of reference counties and the county groups that map to those reference counties.
Read the surrogate description file
SRGDESC and a list of associated spatial surrogate(s) chosen for use in selecting grid cells.
Determine a list of grid cells for each county. Only the selected grid cells are used to estimate the min/max temperatures, 24-hour temperature profiles, and RH over the user-specified modeling period.
Set the dates of the modeling episode in local time using the flags
Determine the averaging method
AVERAGING_METHOD chosen by the user to create 24-hour temperature profiles (i.e., MONTHLY).
Determine the fuel month for the reference county using the
MFMREF input file.
Read the country/state/county
COSTCY file to define the time zones for county groups.
Read the meteorology data that have been processed by MCIP.
Calculate the min/max temperatures hourly and over the modeling period.
Calculate average RH for the specified hour range over the modeling period. The default hour range is from 6 AM to 6 PM local time).
Once min/max temperatures and averaged RH are estimated for all reference counties and all inventory counties in the county groups, estimate diurnal 24-hour temperature profiles for use by the MOVES driver script. The result is a normalized 24-hour shape profile over the user-specified period or fuel month.
When the MOVES model runs for SMOKE, it runs for all emissions processes (or modes), including on-roadway and off-network emissions processes, for the selected pollutants. Off-network emission processes (e.g., parked engine-off, engine starts, and idling, and fuel vapor venting) in MOVES are hour-dependent due to vehicle activity assumptions built into the MOVES model; the emission rate depends on both hour of the day and temperature. On-roadway emission processes (e.g., running exhaust, crankcase running exhaust, brake wear, tire wear, and on-road evaporative), on the other hand, do not depend on hour. In MOVES, these emission processes are categorized into three major groups:
MOVES emission rates are organized into three tables (RPD, RPV, RPP), depending on emission process and whether the vehicle is parked or in motion. The approach to running MOVES for SMOKE is unique for each emission rate table listed in Table 2.4, “MOVES Emission Processes by Emission Rate Tables”. A complete inventory must use the emission rates from all three tables. Note that refueling emission process is not a subject to MOVES emission rate table approach yet.
Table 2.4. MOVES Emission Processes by Emission Rate Tables
|MOVES Lookup Table||Units||smokeProcID||Emissions Process|
|RatePerProfile (RPP)||Grams/vehicle/hour||EFV||Off-network Evaporative Fuel Vapor Venting|
The RPD lookup table is used to provide estimates of on-roadway emissions processes from mobile sources, using a separate file for each reference county. The on-road running processes that appear in this table include running exhaust (EXR), crankcase running exhaust (CXR), brake wear (BRK), tire wear (TIR), on-road evaporative permeation (EPM), on-road evaporative fuel leaks (EFL), and on-road evaporative vapor venting (EFV). The units of the emission rates in this table are grams/mile. The lookup fields for the factors are temperature and average speed. There are 16 set speed bins defined in Table 2.5, “MOVES Default Speed Bins” (i.e., avgSpeedBinID 1=2.5mph, 2=5mph, 3=10mph, …16=75mph). The avgBinSpeed is used for interpolation in the RPD table.
The RPV lookup table is used to provide estimates of off-network emission processes (parked engine-off, engine starts, and idling), except for the evaporative off-network vapor venting emissions process. A separate file is provided for each reference county. The off-network emission processes include start exhaust (EXS), crankcase start exhaust (CXS), off-network evaporative permeation (EPM), off-network evaporative fuel leaks (EFL), extended idle exhaust (EXT), and crankcase extended idle exhaust (CEI). Fuel month, temperature, and local hour are the lookup fields in this table, and hours are in the local time of the modeling county. The units of the emission rates are grams/vehicle/hour. Note: Although the units are grams/vehicle/hour, the number of vehicles (i.e., population) should not be temporally allocated to hours in SMOKE. Instead, a county total of vehicle population should be multiplied by emission rates at any given hour. The number of starts per vehicle by hour is already accounted for in the MOVES lookup table.
The RPP table is used only to estimate emissions for off-network fuel vapor venting (EFV) when the vehicle is parked. This process type includes diurnal (when the vehicle is parked during the day) and hot soak (immediately after a trip when the vehicle parks) emissions types. The process depends on the rate of rise in temperature and the maximum temperature achieved during the day for the diurnal emissions type, and on the hourly temperatures for the hot soak emission type. The lookup fields for this table are reference fuel month and hour of day. As with the RPV table, the units of the emission rates are grams/vehicle/hour. The estimated emissions rates need to be multiplied by the county vehicle population. The reference county lookup tables contain 24-hour emission rates per hour per vehicle using a reference county temperature profile with different minimum and maximum temperatures. The average day county emissions are determined by interpolating between the minimum and maximum temperatures for the modeling county generated by Met4moves. Section 184.108.40.206, “Meteorological Data Processing” summarizes how Met4moves processes meteorological data for both MOVES and SMOKE.
Table 2.5. MOVES Default Speed Bins
|1||2.5||speed < 2.5mph|
|2||5||2.5mph ≤ speed < 7.5mph|
|3||10||7.5mph ≤ speed < 12.5mph|
|4||15||12.5mph ≤ speed < 17.5mph|
|5||20||17.5mph ≤ speed < 22.5mph|
|6||25||22.5mph ≤ speed < 27.5mph|
|7||30||27.5mph ≤ speed < 32.5mph|
|8||35||32.5mph ≤ speed < 37.5mph|
|9||40||37.5mph ≤ speed < 42.5mph|
|10||45||42.5mph ≤ speed < 47.5mph|
|11||50||47.5mph ≤ speed < 52.5mph|
|12||55||52.5mph ≤ speed < 57.5mph|
|13||60||57.5mph ≤ speed < 62.5mph|
|14||65||62.5mph ≤ speed < 67.5mph|
|15||70||67.5mph ≤ speed < 72.5mph|
|16||75||72.5mph ≤ speed|
Table 2.6. MOVES Pollutants associated with SMOKE Emissions Processes (
The following Table 2.7, “MOVES Pollutant Groups” provides a list of available MOVES pollutant groups that the user can specify to model within MOVES. The choice of pollutant groups(s) determines what pollutants are included in the three emission rate lookup tables (RPD, RPV, and RPP) output by MOVES. The letter 'X' marks the key pollutants for inclusion, and a letter 'd' signifies that the pollutant is included in the MOVES run because a key pollutant depends on it. The user modifies the control.in input file to specify the pollutant group.
Table 2.7. MOVES Pollutant Groups
|1||Total Gaseous Hydrocarbons||d||d||d|
|80||Non-Methane Organic Gases||d||d||d|
|86||Total Organic Gases||X||X||X|
|87||Volatile Organic Compounds||X||X||X|
|2||Carbon Monoxide (CO)||X|
|3||Oxides of Nitrogen||X||X|
|31||Sulfur Dioxide (SO2)||X|
|100||Primary Exhaust PM10 - Total||d||X|
|101||Primary PM10 - Organic Carbon||d||X|
|102||Primary PM10 - Elemental Carbon||d||X|
|105||Primary PM10 - Sulfate Particulate||d||X|
|106||Primary PM10 - Brakewear Particulate||X|
|107||Primary PM10 - Tirewear Particulate||X|
|110||Primary Exhaust PM2.5 - Total||X|
|111||Primary Exhaust PM2.5 - Organic Carbon||X|
|112||Primary Exhaust PM2.5 - Elemental Carbon||X|
|115||Primary Exhaust PM2.5 - Sulfate Particulate||X|
|116||Primary Exhaust PM2.5 - Brakewear Particulate||X|
|117||Primary Exhaust PM2.5 - Tirewear Particulate||X|
|91||Total Energy Consumption||d||d||X|
|92||Petroleum Energy Consumption||X|
|93||Fossil Fuel Energy Consumption||X|
|6||Nitrous Oxide (N2O)||X|