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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
×
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Suggested Citation:"6.0 Sensitivity Analysis." National Academies of Sciences, Engineering, and Medicine. 2015. Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report. Washington, DC: The National Academies Press. doi: 10.17226/22212.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

6.0 Sensitivity Analysis As part of this work, a sensitivity analysis was undertaken to test the sensitivity of MOVES outputs to key inputs. The focus was on inputs for which sensitivity findings were not already available. The sensitivity analysis examined the sensitivity of model outputs (emission rates) to the specific input parameters when they are varied across a typical range that might be observed in the real world. This analysis had two objectives: 1) to provide information to MOVES users to help decide whether expending additional effort to gather more detailed local data is worthwhile; and 2) to assist the project team in determining where to focus resources in developing information and sample datasets. The Volpe Center and FHWA completed a sensitivity analysis for regional inputs in 2012 and were performing a similar analysis for project-level inputs, with results expected in 2014. All results in these studies are shown by the 13 source types. EPA has conducted a MOVES sensitivity analysis for temperature and humidity only. ERG also conducted a sensitivity analysis for the Coordinating Research Council (CRC) that examined how MOVES outputs change across the distribution of county-inputs provided by states for the 2011 National Emissions Inventory (NEI). A handful of other analyses conducted by MOVES users were also identified in the literature review and survey conducted in Task 2 of this project. All of these sensitivity analyses were conducted using some version of MOVES2010. There may be minor differences in some impacts if the same analyses were conducted using MOVES2014. The overall conclusions, however, should not change significantly. 6.1 SCENARIOS MODELED Sensitivity analyses were performed on the following MOVES inputs: • Source type population (Scenarios 1-4). Independent of other inputs, source type population primarily influences off-network nonrunning emissions (e.g., start, evaporative, extended idle). Because there can be considerable effort in developing this input to accurately reflect all 13 source types, the project team examined the impacts of uncertainty in specific source type population fractions. Four input datasets were defined that reflect different amounts of light- versus heavy-duty vehicles (Scenario 1), passenger cars versus light- duty trucks (Scenario 2), single-unit versus combination trucks (Scenario 3), and short- versus long-haul trucks (Scenario 4). • Road type and average speed distributions (Scenarios 5 and 6). For these input tables two input data sets were defined that illustrate varying levels of 6-1

source type information, as described in Table 6.1. All other variables were held constant. • Month, day-of-week, and hour VMT fraction temporal adjustments (Scenarios 7-9). The effects of time-of-day and seasonal distributions on emissions depend upon variations in temperature and humidity over the day or across seasons. Alternative input data sets were tested reflecting different month VMT fractions and hour VMT fractions to illustrate the importance of more detailed temporal adjustments. These specific percentage adjustments are listed in Table 6.1. • Grade (Scenarios 10-15). Road grade is a new input for MOVES and not all users are familiar with data sources to develop this input or know what its impact might be. The project team selected six different scenarios to illustrate the effects of grade on emissions from different source types, ranging from -6 percent to +6 percent grade in 2 percent intervals. For each of these scenarios, MOVES was run with alternative input datasets and the percentage differences in results of total emissions (running and nonrunning) for key pollutants (VOC, CO, NOx, CO2, and PM10)2 compared across the range of inputs. The percent change in emissions for each pollutant was computed relative to the emissions using base case inputs as described in the next section. For Scenarios 1-4, VMT was adjusted in addition to population. This was accomplished by taking the miles per vehicle ratio from the base case, modifying the population for each case, and multiplying the base ratio by the modified population to arrive at representative VMT. The road grade results (Scenarios 10-15) do not include evaporative emissions because MOVES project-level outputs do not include these emissions. Table 6.1 summarizes the scenarios. 2 While the sensitivity analysis was run with PM10 as the output, the percentage impacts should be identical or nearly identical for PM2.5. 6-2

Table 6.1 Scenarios for Sensitivity Testing Input Scenario No. Description Source Type Population 1 Double the percentage of vehicles within heavy-duty source types (41-62) and reduce light- duty vehicles (11-32) by the amount of the heavy-duty increase. 2 Shift 20% of passenger cars from passenger cars (21) to passenger trucks (31). 3 Shift 25% of trucks (source types 51-62) from single-unit trucks (52 and 53) to combination trucks (61 and 62). 4 Shift 25% of trucks from short-haul trucks (52 and 61) to long-haul trucks (53 and 62). Source Type Detail 5 Make the road type distribution the same for all source types (as opposed to the MOVES national defaults, which have different road type distributions by six HPMS vehicle types). The road type distribution for passenger cars (21) was applied to all vehicle types. 6 Change Average Speed Distribution input to account for slower relative speed of trucks compared to light-duty vehicles. Made heavy-duty vehicles (40-60) 5 mph slower than light- duty (10-30). Since speed bins in the model are demarcated in 5 mph increments, this was done by setting speed bin 16 to zero, adding speed bins 1 and 2 together, and shifting remaining fractions down one speed bin. Temporal Adjustments (month and hour VMT fractions) 7 Change Month VMT Fractions to make summer (June to August) account for 5% more than MOVES defaults (27.4%). Decreased equal amount from all other months. 8 Change Month VMT Fractions to make winter (December to February) account for 5% more than MOVES defaults (22.3%). Decreased equal amount from all other months. 9 Change Hour VMT Fractions to show more overnight and early morning traffic (11% more on weekdays, 9% more on weekends for 8 p.m. to 8 a.m. time intervals). Road Grade 10-15 Road Grade = -6%, -4%, -2%, +2%, +4%, +6%. Repeated for urban restricted and unrestricted access road types. 6.2 BASE CASE INPUTS The following base cases were used: Scenarios 1-6 were compared to a nationwide July weekday base case, while Scenarios 7-9 were compared to a nationwide annual base case. Scenarios 10-15 were compared to a project-level base case. The base cases depended heavily upon national default values embedded in MOVES. In Scenarios 7-9, the analysis was run for two counties – Suffolk, Massachusetts and Harris, Texas, since the widely varying meteorological inputs across counties could wash out temporal effects when run at the national scale. Scenario 7 was run for Harris County, to test the effects of a shift towards more summer VMT in a hot climate, and Scenario 8 was run for Suffolk County, to test the effects of a shift towards more winter VMT in a colder climate. Table 6.2 shows the specific base case assumptions used for each scenario. 6-3

Table 6.2 Base Case Inputs Parameter Scenarios 1-6 Scenarios 7-9 Scenarios 10-15 Year 2010 2010 2020a Month July All months July Day Weekday Weekday and weekend Weekday Hour All 24 hours All 24 hours Noon to 1 p.m. Geographic Bounds Nation Suffolk County, Massachusetts and Harris County, Texas Washtenaw County, Michigan Road Type(s) All All Urban arterial and urban highway Vehicles/Fuel Type All combination of gasoline and diesel vehicles available in MOVES plus CNG transit buses Age Distribution 1999 National defaults 1999 National defaults County default Average Speed Distribution National default National default N/A Fuel National default Local default County default Road Type Distribution National default National default N/A Ramp Fraction National default National default N/A I/M Program National default Local default County default Vehicle Type VMT National default Local default N/A Source Type Population National default National default N/A Temperature National default Local default Local default Humidity National default Local default Local default Links N/A N/A 2 links, 0.5-mile length, 500 vehicle volume, 30 mph average speed, road types 4 and 5 Link Source Type N/A N/A 2 links, derived from EPA project- level MOVES example Link Drive Schedule N/A N/A Default a 2020 was selected rather than 2010 because the project-level scenarios were based on an EPA project-level example using 2020 inputs, and the post-2012 fuel type inputs are simpler. 6-4

6.3 OUTPUT SUMMARIES BY SCENARIO TYPE The following section presents summary tables for each model input that was varied. Supporting data are provided in Section 6.5. Source Type Populations Table 6.3 shows the effects of source type population on emissions (Scenarios 1-4). Table 6.3 Effects of Source Type Population on Emissions Scenario Description VOC CO NOx CO2 PM10 1 – Light- versus heavy-duty vehicles Double the number of vehicles within heavy- duty source types (40-60) and reduce light- duty vehicles (10-30) correspondingly. 6.90% 4.40% 35.60% 19.72% 66.30% 2 – Passenger cars versus trucks Shift 20% of passenger vehicles from passenger cars (21) to passenger trucks (31). 1.59% 2.41% 1.16% -0.06% 0.67% 3 – Single-unit versus combination trucks Shift 25% of trucks from single unit trucks (52 and 53) to combination trucks (61 and 62). 2.21% -0.40% 13.65% 8.52% 22.89% 4 – Short-haul versus long-haul trucks Shift 25% of trucks from short-haul trucks (52 and 61) to long-haul trucks (53 and 62). 2.12% -0.42% 7.77% 5.66% 9.70% Note: Table shows the percent change in composite emissions (all source types) compared with a base case of national source type distribution embedded in MOVES. Scenario 1 doubles the fraction of heavy-duty vehicles from 4.4 to 8.8 percent. This results in a substantial increase in NOx, CO2, and PM10 emissions (up to 66 percent) and a modest to moderate increase in VOC and CO emissions of 4 to 7 percent.3 Scenario 2 decreases the fraction of passenger cars and increases the fraction of passenger trucks by about 9 percent of all vehicles. The impact is modest, with all pollutants increasing by less than 3 percent. Scenario 2 shows a slight reduction in CO2 emissions – a counterintuitive outcome since light trucks on average have lower fuel economy and higher CO2 emissions than passenger cars. This is because in all scenarios, emissions may change not only because of the differences in emission rates between vehicle types, but also because of differences in the average distance driven per vehicle. For example, passenger trucks are driven about 30 percent less, on average, than 3 In this discussion, “modest” means less than 5 percent; “moderate” means 5 to 15 percent; “substantial” means 15 to 50 percent; and “very substantial” means greater than 50 percent. 6-5

passenger cars (as represented in the MOVES default data – 30.8 versus 43.3 miles per vehicle per day). For passenger trucks versus cars driven the same distance, the emissions differences would be higher than those shown. MOVES users should ensure that VMT fractions reflect actual distances driven by vehicle type, rather than source type populations. Scenario 3 reduces the number of single-unit trucks by about six-tenths of a percent of all vehicles, and increases the number of combination trucks by the same amount. The impact is a moderate to substantial increase in NOx, CO2, and PM10 (up to 23 percent). Changes in VOC and CO are modest. The slight reduction in CO is likely due to the larger fraction of diesel vehicles in the combination truck category, compared to single-unit trucks which include a substantial fraction of gasoline vehicles. Scenario 4 reduces the number of short-haul trucks by about six-tenths of a percent of all vehicles, and increases the number of long-haul trucks by the same amount. The impact is a moderate increase in NOx, CO2, and PM10 of up to 10 percent. Changes in VOC and CO are modest. The impact of shifts in the heavy-duty vehicle population segment is greater than might be expected considering only the fraction of the vehicle population. This is because heavy-duty vehicles are driven much longer distances per vehicle, on average, than light-duty vehicles. For example, while the base source-type fraction of heavy-duty vehicles is 4.4 percent, the base VMT fraction is 7.6 percent. While only one set of alternative assumptions was analyzed for each pollutants, the results of different assumptions should be linear: for example, shifting 50 percent of trucks from single-unit to combination, instead of 25 percent, should double the NOx increase to about 27 percent. Road Type and Average Speed Distributions Table 6.4 shows the effects of road type and average speed distributions by source type on emissions. Changing the road type distribution to be the same for all source types (Scenario 5) has a modest impact on all pollutants except PM, for which the impact is moderate (around 10 percent in this scenario). If the average speed distribution is adjusted to assume that trucks travel slower than other vehicles (Scenario 6), the impact is roughly a 6 percent increase in PM10 and a 1 to 2 percent increase in other pollutants. 6-6

Table 6.4 Effects of Road Type and Average Speed Distributions by Source Type on Emissions Scenarios Description VOC CO NOx CO2 PM10 5 – Road Type Distribution Make the road type distribution the same for all source types as opposed to the MOVES national embedded distributions. 1.88% 0.64% 3.88% 1.83% 10.42% 6 – Average Speed Distribution Reduce heavy-duty vehicle speed distribution by 5 mph. 1.22% 0.43% 2.36% 1.09% 5.67% Note: Table shows the percent change in composite emissions (all source types) compared with a base case of national road type and speed distributions embedded in MOVES. Figure 6.1 illustrates the road type distributions in the default (MOVES embedded assumptions) and Scenario 5 (uniform distribution) scenarios. Scenario 5 results will be driven by differences in road type distributions for trucks compared to the Scenario 5 uniform case, which is the same as the distribution for cars. For example, the MOVES defaults show a higher fraction of truck traffic on rural roads compared to Scenario 5. The increase in emissions in Scenario 5 may be largely due to the greater amounts of travel on urban roadway with low speeds and high emission rates (left side of the U-shaped emission rate curve) and especially urban unrestricted access roads, which involve more transient driving. Figure 6.1 MOVES Embedded Road Type Distributions versus Scenario 5 0% 10% 20% 30% 40% 50% 60% Rural Restricted Access Rural Unrestricted Access Urban Restricted Access Urban Unrestricted Access MC Car Light Truck Bus Single Truck Combo Truck Case 5 - Uniform 6-7

Temporal Adjustments Table 6.5 shows the effects of temporal adjustments on emissions. Changing the month fractions has a very modest effect on emissions of all pollutants – less than 1 percent in nearly all cases, except for PM10 in the cold climate winter month shift, which increased by about 2 percent. Changing the hour VMT fractions also had a very modest effect on overall emissions – about 1 percent or less for all pollutants for the scenario analyzed. While larger impacts will likely be seen for episodic events (e.g., very hot summer days), these results suggest that the effects of temporal distributions on annual emissions at a regional scale will be very modest. The direction of the effect varies by pollutant since different pollutants are affected differently by the temperature and humidity changes that occur across hours and months. Table 6.5 Effects of Temporal Adjustments on Emissions Scenario Description VOC CO NOx CO2 PM10 7 – Month Fractions (Summer) Change Month VMT Fractions to make summer (June to August) account for 5% more than MOVES defaults (27.4%). Decrease equal amount from all other months. (Harris County, Texas) 0.08% 0.75% 0.10% 0.42% -0.42% 8 – Month Fractions (Winter) Change Month VMT Fractions to make winter (December to February) account for 5% more than MOVES defaults (22.3%). (Suffolk County, Massachusetts) 0.03% 0.67% 0.30% -0.07% 1.90% 9 – Hour Fractions Change Hour VMT Fractions to show more overnight and early morning traffic (8 p.m. to 8 a.m., 11% more on weekdays, 9% more on weekends). (Harris County, Texas and Suffolk County, Massachusetts) -0.29% -0.21% -1.05% -0.36% -1.07% -0.40% -0.75% -0.44% 0.39% 0.97% Note: Table shows the percent change in composite emissions (all source types) compared with a base case of road type and speed distributions embedded in MOVES. Road Grade Figures 6.2 and 6.3 show the effects of road grade on emissions. The impact is substantial or very substantial at all grades tested, with emissions decreasing by up to about half on downhill grades, and increasing by 50 to 100 percent or more on steeper uphill grades. Impacts are of similar magnitude for unrestricted and restricted access roadways. 6-8

Figure 6.2 Percent Change in Emissions by Road Grade Urban Unrestricted Access Roads Note: Figure shows the percent change in composite emissions (all source types) compared with a base case of zero percent road grade. Emissions are for a 0.5-mile roadway link with average speed 30 mph. Figure 6.3 Percent Change in Emissions by Road Grade Urban Restricted Access Roads Note: Figure shows the percent change in composite emissions (all source types) compared with a base case of zero percent road grade. Emissions are for a 0.5-mile roadway link with average speed 30 mph. -100% -50% 0% 50% 100% 150% 200% -6% -4% -2% 2% 4% 6% VOC CO NOx CO2 PM10 -100% -50% 0% 50% 100% 150% 200% -6% -4% -2% 2% 4% 6% VOC CO NOx CO2 PM10 6-9

6.4 COMPARISON WITH PREVIOUS SENSITIVITY ANALYSIS Table 6.6 presents the results of this sensitivity analysis alongside the results of the sensitivity analyses conducted by the Volpe Center for FHWA,4 by EPA staff,5 and by ERG for the CRC.6 The factors analyzed in this analysis were specifically chosen to fill in gaps from the Volpe work (the CRC research was published after the analysis was conducted). The focus here is on fleetwide composite emissions across all source types, whereas the Volpe study showed how emissions varied for each source type. The Volpe study also looked at running emissions only for most pollutants, with start emissions evaluated separately for meteorological inputs. The results presented here combine emissions from different processes. The EPA study looked specifically at the impact of meteorological inputs on emissions for gasoline and diesel vehicles. Emissions impacts in Table 6.6 are characterized as “modest” (less than 5 percent), “moderate” (5 to 15 percent), “substantial” (15 to 50 percent), and “very substantial” (greater than 50 percent) compared to the indicated base case. Because presenting data for 13 source types would be overwhelming, representative results from the Volpe study are presented for passenger cars (PC) and long-haul combination trucks (CT). 4 Noel, G., and R. Wayson (2012). MOVES2010a Regional-Level Sensitivity Analysis. Volpe National Transportation Systems Center, prepared for Federal Highway Administration, DOT-VNTSC-FHWA-12-05. 5 Choi, D., et al (undated). MOVES Sensitivity Analysis: The Impacts of Temperature and Humidity on Emissions. U.S. Environmental Protection Agency. 6 Coordinating Research Council Project A-84: Study of MOVES Inputs for the National Emissions Inventory. 6-10

Some key findings from the various studies include: • Age distribution has a substantial impact for passenger cars and a moderate impact for trucks. • For source-type populations, the most important parameter is the split of light- versus heavy-duty vehicles. Single-unit versus combination trucks can be important for NOX and PM, and short- versus long-haul split has somewhat lesser but still moderate importance for these pollutants. Impacts of truck splits on VOC are modest. • The effects of temporal adjustments (month and hour fractions) on annual emissions at a regional scale will be very modest. • Changing the road type distribution by source type has a modest to moderate impact. • Changing ramp fractions has a modest impact on all pollutants, except the impact on passenger car PM is substantial. • Changing the average speed distribution to reflect different congestion levels can have a substantial impact on most pollutants for both cars and trucks. The impact is less significant for NOX than for VOC and PM. • Road grades have a substantial or very substantial impact on all pollutants. • The impact of meteorology (temperature and humidity) varies greatly depending upon the pollutant, process, source type, and temperature range. 6-11

Table 6.6 Combined Sensitivity Analysis Results MOVES Input Source Base Case Comparison Made VOC NOx PM Fleet Inputs Age Distribution by Vehicle Class Volpe/FHWA 2010 National Default Age Distribution Move 10% of vehicles to Group 1 (0-10 years); Move 10% of vehicles to Group 2 (11-20 years); Move 5% of vehicles to Group 3 (21-30 years); completed for several vehicle types PC: Substantial (-29% to +24%) CT: Moderate (-5% to +6%) PC: Substantial (-20% to +16%) CT: Moderate (-9% to +9%) PC: Substantial (-19% to +21%) CT: Moderate (-7% to +7%) Age Distribution by Vehicle Class ERG/CRC Submittals for 2011 NEI Increase average age from 10th to 90th percentile Very Substantial (+55% HC) Substantial (+40%) Substantial (+45%) Source (Vehicle) Type Population: Light versus Heavy- Duty Vehicles CS/ERG 2010 National Default Source Type Distribution Double HD vehicles and reduce LD vehicles correspondingly Moderate (+7%) Substantial (+36%) Very substantial (+66%) Passenger Cars versus Trucks Shift 20% of passenger vehicles from cars (21) to trucks (31) Modest (+2%) Modest (+1%) Modest (+1%) Single-Unit versus Combination Trucks Shift 25% of trucks from single unit to combination Modest (+2%) Moderate (+14%) Substantial (+23%) Short-Haul versus Long-Haul Trucks Shift 25% of trucks from short- haul to long-haul Modest (+2%) Moderate (+8%) Moderate (+10%) Source (Vehicle) Type Population: ERG/CRC Submittals for 2011 NEI Increase source type fraction of total population from 10th to 90th percentile Substantial (+45% HC) Moderate (+14%) Moderate (+14%) Regional Activity Inputs Regional VMT by vehicle class ERG/CRC Submittals for 2011 NEI Increase HPMS type fraction of total VMT from 10th to 90th percentile Substantial (+40% HC) Very Substantial (+110%) Very Substantial (+150%) Temporal Adjustments: Month VMT Fractions CS/ERG Default Month Distribution Change Month VMT Fractions to make summer (Jun-Aug) or winter (Dec-Feb) account for 5% more than MOVES defaults (27.4%). Decrease equal amount from all other months Modest (<1%) Modest (<1%) Modest (<2%) 6-12

MOVES Input Source Base Case Comparison Made VOC NOx PM Hour VMT Fractions CS/ERG Default Hour Distribution Change Hour VMT Fractions to show more overnight traffic (8 p.m.-7 a.m., 11% more on weekdays, 9% more on weekends) Modest (<1%) Modest (<1%) Modest (<1%) Regional Activity Inputs (continued) Road Type Distribution CS/ERG MOVES National Embedded Distributions Make the road type distribution the same for all source types Modest (+2%) Modest (+4%) Moderate (+10%) Ramp Fraction Volpe/ FHWA National Default (0.08) 0, 0.02, 0.04, 0.06, 0.10, 0.12 0.16, 0.20 Modest (-3% to +4%) Modest (-2% to +3%) PC: Substantial (-15% to +22%) CT: Modest (-3% to +5%) Average Speed Distribution Volpe/ FHWA National Default Speed Distribution for Urban Interstate LOS B, C, D, E, F PC: Substantial (-14% to +33%) CT: Substantial (-29% to +49%) PC: Moderate (-1% to +6%) CT: Substantial (-6% to +21%) PC: Substantial (-6% to -16%) CT: Substantial (-20% to +53%) Average Speed Distribution CS/ERG Reduce HD vehicle speed by 5 mph Modest (+1%) Modest (+2%) Moderate (+6%) Average Speed Distribution ERG/CRC Submittals for 2011 NEI Decrease average speed from 90th to 10th percentile Moderate (+8% HC) Moderate (+10%) Substantial (+16%) Project-Level Inputs Project-Level Link Activity (Average Speed, Drive Schedules, or Operating Mode Distributions) Volpe/ FHWA TBD Off-Network Data (Start Fraction, Extended Idle Fraction, Parked Fraction) Volpe/ FHWA TBD Link Characteristics: Grade CS/ERG 0% Grade, Urban Restricted and Unrestricted Road Types, 30 mph -6%, -4%, -2%, +2%, +4%, +6% grade 2%: Substantial (-15% to +22%) 6%: Substantial to very substantial (-36% to +92%) 2%: Substantial (-26% to +33%) 6%: Substantial to very substantial (-58% to +118%) 2%: Substantial (-27% to +41%) 6%: Very substantial (-55% to +175%) 6-13

MOVES Input Source Base Case Comparison Made VOC NOx PM Link Source Types (Hour Fraction) TBD Other Inputs Weather – Meteorology Data Volpe/ FHWA 60º F -40º, -20º, 0º, 20º, 40º, 60º, 80º, 100º, 120º F Running: PC: Substantial above 60º F (up to 17%); no impact below. CT: No impact Starts: Substantial below 80º F; no impact above Running: Substantial between 40 and 100º F (-20% to +32%); no impact outside that range Starts: Very Substantial at all temps below 80º F (>100%) PC: Very substantial below 60º F (>100%); no impact above 80º F CT: Modest (<0.1%) Volpe/ FHWA 50% Relative Humidity 0%, 20%, 40%, 50%, 60%, 80%, 100% (Nox at 60º F and 80º F, all others at 80º F) PC: Modest (-1% to +2%) CT: Modest (<1%) Moderate (-12% to +15%) Modest (<1%) EPA 75º F -40º F to 120º F in 10º increments; Calendar years 2005, 2015, and 2025 Very substantial for gasoline (~+50-70%), Substantial for diesel (~+10-30%) at 20º F Moderate for gasoline (~+5-8%, Substantial for diesel (~+15-18%) at 20º F Very substantial (~+400- 600% at 20º F) for gasoline Modest (<1%) for diesel EPA 0% Relative Humidity 0-100% relative humidity in 10% increments for 6-12 different temperatures Modest (up to ~+5%) Substantial (up to ~-25%) Modest (<1%) Inspection/Maintenance (I/M) Programs N/A Fuel Formulation and Supply N/A Note 1: Modest = <5%; Moderate = 5-15%; Substantial = 15-50%; Very Substantial = >50%. Note 2: Unless noted, Volpe/FHWA results are for running emissions for passenger cars (PC) and combination trucks (CT). CS/ERG results are for combined vehicle fleet and all processes. EPA results are for gasoline versus diesel for all source types. 6-14

Table 6.7 provides a summary of MOVES inputs by sensitivity level. It takes the worst case result for each MOVES input from Table 6.6 and assigns it to one of the four sensitivity ranges. This was done separately for VOC, NOx, and PM. In general temperature, VMT, speed, age, and population have either substantial or very substantial sensitivity for all three pollutants. The data sources that are critical for these inputs include registration data for age and population inputs; classified traffic counts and travel demand models for VMT; and real-world and/or modeled speed data. Month and hour VMT fraction inputs (based on seasonal and hourly traffic data) have modest sensitivity for all pollutants. Ramp fraction and source type detail for road type distributions and speeds have different sensitivity depending on the pollutant of concern. Table 6.7 Summary of MOVES Inputs Falling in Different Sensitivity Ranges Sensitivity Range VOC NOx PM Very Substantial (>50%) Temperature, Speed, Age Temperature, VMT, Speed Temperature, VMT, Speed Substantial (15-50%) Population, VMT Population, Age, Humidity Population, Age, Ramp Fraction Moderate (5-15%) None None Source type detail for road type dist. and speed Modest (<5%) Source type detail for road type dist. and speed, Month VMT Fraction, Hour VMT Fraction, Ramp Fraction Source type detail for road type dist. and speed, Month VMT Fraction, Hour VMT Fraction, Ramp Fraction Month VMT Fraction, Hour VMT Fraction, Humidity Note: The worst case sensitivity results are used for assigning inputs to the ranges in this table. 6-15

6.5 INPUT AND OUTPUT DATA This section provides additional detail on inputs and outputs. Table 6.8 Emissions by Source Type Base Case for Scenarios 1-6 ID Source Type Base Source Type Fract. Base VMT Fract. Tons g/mi VOC CO NOx CO2 PM10 VOC CO NOx CO2 PM10 11 Motorcycle 3.60% 0.53% 272 737 34 20,286 1.5 5.03 13.63 0.63 375 0.03 21 Passenger Car 46.52% 54.42% 2,586 25,845 3,969 2,150,857 43.3 0.47 4.67 0.72 389 0.01 31 Passenger Truck 34.10% 28.32% 2,283 24,742 3,539 1,564,188 40.9 0.79 8.59 1.23 543 0.01 32 Light Commercial Truck 11.39% 9.46% 779 8,539 1,568 535,450 33.7 0.81 8.88 1.63 557 0.03 41 Intercity Bus 0.05% 0.09% 6 39 124 16,325 7.0 0.71 4.39 13.87 1,826 0.78 42 Transit Bus 0.03% 0.03% 2 23 27 3,999 1.4 0.72 7.63 9.17 1,342 0.48 43 School Bus 0.34% 0.10% 9 119 68 10,143 4.0 0.91 11.78 6.74 1,007 0.4 51 Refuse Truck 0.03% 0.06% 4 30 61 11,429 3.5 0.69 4.67 9.47 1,771 0.54 52 Single-Unit Short-Haul Truck 2.12% 2.18% 268 3,517 1,105 239,096 53.0 1.21 15.86 4.98 1,078 0.24 53 Single-Unit Long-Haul Truck 0.27% 0.37% 24 281 123 38,117 4.9 0.64 7.48 3.28 1,017 0.13 54 Motor Home 0.49% 0.13% 29 397 66 14,704 2.0 2.11 29.26 4.86 1,083 0.15 61 Combination Short-Haul Truck 0.48% 1.63% 86 448 1,619 342,902 80.4 0.52 2.7 9.75 2,064 0.48 62 Combination Long-Haul Truck 0.57% 2.67% 302 777 2,492 616,763 95.0 1.12 2.86 9.19 2,275 0.35 Note: Tons are for a July weekday. Grams/mile are converted from tons divided by miles traveled on a July weekday, by source type. 6-16

Table 6.9 Emissions by Source Type – Scenario 1 Double Heavy-Duty Vehicles ID Source Type Base Source Type Fract. Base VMT Fract. Tons VOC CO NOx CO2 PM10 11 Motorcycle 3.44% 0.49% 259 703 32 19,354 1.4 21 Passenger Car 44.38% 50.41% 2,468 24,658 3,787 2,052,076 41.4 31 Passenger Truck 32.53% 26.23% 2,178 23,605 3,376 1,492,350 39.0 32 Light Commercial Truck 10.87% 8.76% 744 8,147 1,496 510,859 32.1 41 Intercity Bus 0.10% 0.17% 13 79 248 32,650 13.9 42 Transit Bus 0.06% 0.06% 4 45 55 7,998 2.8 43 School Bus 0.69% 0.19% 18 237 136 20,286 8.0 51 Refuse Truck 0.06% 0.12% 9 60 122 22,857 6.9 52 Single-Unit Short- Haul Truck 4.24% 4.24% 535 7,034 2,210 478,192 106.1 53 Single-Unit Long- Haul Truck 0.54% 0.72% 48 561 246 76,234 9.7 54 Motor Home 0.98% 0.26% 57 794 132 29,409 4.0 61 Combination Short- Haul Truck 0.96% 3.17% 173 896 3,238 685,804 160.8 62 Combination Long- Haul Truck 1.15% 5.18% 605 1,553 4,983 1,233,527 190.0 Note: Tons are for a July weekday. Grams/mile values are not shown because they are the same as the Base Case (Table 6.7). 6-17

Table 6.10 Emissions by Source Type – Scenario 2 Shift Passenger Cars to Passenger Trucks ID Source Type Base Source Type Fract. Base VMT Fract. Tons VOC CO NOx CO2 PM10 11 Motorcycle 3.60% 0.55% 272 737 34 20,286 1.5 21 Passenger Car 37.21% 44.96% 2,069 20,676 3,175 1,720,685 34.7 31 Passenger Truck 43.40% 37.22% 2,906 31,492 4,504 1,990,964 52.1 32 Light Commercial Truck 11.39% 9.77% 779 8,539 1,568 535,450 33.7 41 Intercity Bus 0.05% 0.09% 6 39 124 16,325 7.0 42 Transit Bus 0.03% 0.03% 2 23 27 3,999 1.4 43 School Bus 0.34% 0.10% 9 119 68 10,143 4.0 51 Refuse Truck 0.03% 0.07% 4 30 61 11,429 3.5 52 Single-Unit Short- Haul Truck 2.12% 2.25% 268 3,517 1,105 239,096 53.0 53 Single-Unit Long-Haul Truck 0.27% 0.38% 24 281 123 38,117 4.9 54 Motor Home 0.49% 0.14% 29 397 66 14,704 2.0 61 Combination Short- Haul Truck 0.48% 1.69% 86 448 1,619 342,902 80.4 62 Combination Long- Haul Truck 0.57% 2.75% 302 777 2,492 616,763 95.0 Note: Tons are for a July weekday. Grams/mile values are not shown because they are the same as the Base Case (Table 6.7). 6-18

Table 6.11 Emissions by Source Type – Scenario 3 Shift Single-Unit to Combination Trucks ID Source Type Base Source Type Fract. Base VMT Fract. Tons VOC CO NOx CO2 PM10 11 Motorcycle 3.60% 0.52% 272 737 34 20,286 1.5 21 Passenger Car 46.52% 53.46% 2,586 25,845 3,969 2,150,857 43.3 31 Passenger Truck 34.10% 27.82% 2,283 24,742 3,539 1,564,188 40.9 32 Light Commercial Truck 11.39% 9.29% 779 8,539 1,568 535,450 33.7 41 Intercity Bus 0.05% 0.09% 6 39 124 16,325 7.0 42 Transit Bus 0.03% 0.03% 2 23 27 3,999 1.4 43 School Bus 0.34% 0.10% 9 119 68 10,143 4.0 51 Refuse Truck 0.03% 0.06% 4 30 61 11,396 3.5 52 Single-Unit Short- Haul Truck 1.59% 1.60% 200 2,634 827 178,813 39.7 53 Single-Unit Long-Haul Truck 0.20% 0.27% 18 210 92 28,506 3.6 54 Motor Home 0.49% 0.13% 29 396 66 14,662 2.0 61 Combination Short- Haul Truck 0.75% 2.52% 135 702 2,537 537,254 126.0 62 Combination Long- Haul Truck 0.90% 4.10% 474 1,217 3,904 966,336 148.8 Note: Tons are for a July weekday. Grams/mile values are not shown because they are the same as the Base Case (Table 6.7). 6-19

Table 6.12 Emissions by Source Type – Scenario 4 Shift Short-Haul to Long-Haul Trucks ID Source Type Base Source Type Fract. Base VMT Fract. Tons VOC CO NOx CO2 PM10 11 Motorcycle 3.60% 0.53% 272 737 34 20,286 1.5 21 Passenger Car 46.52% 53.80% 2,586 25,845 3,969 2,150,857 43.3 31 Passenger Truck 34.10% 28.00% 2,283 24,742 3,539 1,564,188 40.9 32 Light Commercial Truck 11.39% 9.35% 779 8,539 1,568 535,450 33.7 41 Intercity Bus 0.05% 0.09% 6 39 124 16,325 7.0 42 Transit Bus 0.03% 0.03% 2 23 27 3,999 1.4 43 School Bus 0.34% 0.10% 9 119 68 10,143 4.0 51 Refuse Truck 0.03% 0.06% 4 29 59 11,114 3.4 52 Single-Unit Short- Haul Truck 1.59% 1.57% 197 2,602 807 174,435 38.7 53 Single-Unit Long- Haul Truck 0.48% 0.63% 41 488 211 65,521 8.4 54 Motor Home 0.49% 0.13% 28 390 64 14,303 1.9 61 Combination Short- Haul Truck 0.36% 1.18% 63 328 1,183 250,589 58.8 62 Combination Long- Haul Truck 1.02% 4.54% 521 1,339 4,290 1,062,078 163.6 Note: Tons are for a July weekday. Grams/mile values are not shown because they are the same as the Base Case (Table 6.7). 6-20

Figure 6.4 VMT Fractions by Scenario for Source Type Shifts Table 6.13 Emissions for Different Road Type and Average Speed Distributions Scenarios 5 and 6 Scenario Description Tons Grams/mile VOC CO NOx CO2 PM10 VOC CO NOx CO2 PM10 0 Base Case 6,651 65,493 14,795 5,564,259 371 0.654 6.442 1.455 547 0.036 5 Road Type Variation 6,777 65,910 15,368 5,666,100 409 0.666 6.475 1.510 557 0.040 6 Decrease in Truck Speed 6,733 65,775 15,144 5,624,660 392 0.662 6.470 1.490 553 0.039 Note: Tons are for a July weekday. Grams/mile are converted from tons divided by miles traveled on a July weekday, by source type. 0% 10% 20% 30% 40% 50% 60% 11 21 31 32 41 42 43 51 52 53 54 61 62 MOVES Source Type Base Case Scenario 1 Scenario 2 Scenario 3 Scenario 4 6-21

Table 6.14 Month Distributions (Percent of VMT by Month) Scenarios 7 and 8 Month Base 5% Increase Summer (Scenario 7) 5% Increase Winter (Scenario 8) 1 7.3% 6.8% 9.0% 2 7.0% 6.4% 8.6% 3 8.2% 7.6% 7.6% 4 8.2% 7.7% 7.7% 5 8.8% 8.2% 8.2% 6 8.8% 10.5% 8.3% 7 9.2% 10.9% 8.7% 8 9.3% 11.0% 8.8% 9 8.5% 7.9% 7.9% 10 8.7% 8.1% 8.1% 11 8.0% 7.5% 7.5% 12 8.0% 7.5% 9.7% Figure 6.5 Example of Hour Distribution Shift Scenario 9 Note: Shown for passenger cars, road type 5 (urban unrestricted access), weekday. Distributions for other road types and source types are similar. 0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Percent of Daily VMT Base Case Scenario 9 6-22

Table 6.15 Effects of Road Grade Road Type Grade VOC CO NOx CO2 PM10 Unrestricted Access -6% -36% -59% -58% -41% -55% -4% -28% -45% -45% -31% -45% -2% -16% -26% -26% -17% -27% +2% 22% 36% 33% 22% 41% +4% 50% 81% 69% 47% 94% +6% 91% 162% 110% 72% 175% Restricted Access -6% -34% -59% -60% -43% -55% -4% -26% -44% -47% -32% -44% -2% -16% -28% -28% -18% -27% +2% 22% 31% 34% 21% 37% +4% 55% 85% 75% 47% 88% +6% 92% 160% 118% 74% 154% Note: Table shows the percent change in composite emissions (all source types) compared with a base case of zero percent road grade. Emissions are for a 0.5-mile roadway link with average speed of 30 mph. 6-23

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Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report Get This Book
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TRB’s National Cooperative Highway Research Program (NCHRP) Web-Only Document 210: Input Guidelines for Motor Vehicle Emissions Simulator Model, Volume 3: Final Report documents the research process for developing the Practitioners’ Handbooks and tools, and provides additional documentation not included in the handbook.

NCHRP Web-Only Document 210 Volume 1: Practitioners’ Handbook: Regional Level Inputs explores the development of inputs for a “regional” (county, multicounty, or state) level of application. NCHRP Web-Only Document 210 Volume 2: Practitioners’ Handbook: Project Level Inputs explores the development of inputs for a project level of analysis, using the Project Domain/Scale of the Motor Vehicle Emission Simulator (MOVES) model.

Example dataset 1, example dataset 2, example dataset 3, and the MOVES tools are available for download. Please note that these files are large and may take some time to download.

Software is offered as is, without warranty or promise of support of any kind either expressed or implied. Under no circumstance will the National Academy of Sciences or the Transportation Research Board (collectively “TRB”) be liable for any loss or damage caused by the installation or operations of this product. TRB makes no representation or warrant of any kind, expressed or implied, in fact or in law, including without limitation, the warranty of merchantability or the warranty of fitness for a particular purpose, and shall not in any case be liable for any consequential or special damages.

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