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.

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.

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:

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:

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.