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(Revised and updated, July 2013

EMISSION INVENTORY SOURCE CATEGORY

Miscellaneous Processes / Road Dust

EMISSION INVENTORY CODES (CES CODES) AND DESCRIPTION

640-635-5400-0000 (83618) Paved Entrained Road Dust - Freeways

640-637-5400-0000 (83626) Paved Entrained Road Dust - Major Streets

640-639-5400-0000 (83634) Paved Entrained Road Dust - Collector Streets

640-641-5400-0000 (83642) Paved Entrained Road Dust - Local Streets

640-643-5400-0000 (89656) Paved Entrained Road Dust - Rural Streets

640-636-5400-0000 (47456) Paved Entrained Road Dust - Unspecified Paved Roads

METHODS AND SOURCES

The paved road dust category includes emissions of particulate matter (PM) from 

resuspended road surface material that is entrained by vehicular travel on public and 

industrial paved roads. Entrained paved road dust, or fugitive dust, contributes to airborne 

PM emissions throughout California. Because it is not feasible to directly measure 

region-wide emissions from travel on paved roads, ARB computes emissions using the 

emission factor equation provided in the Final Section of the Fifth Edition, Volume 1, 

Chapter 13.2.1, of the U.S. EPA’s AP-42 document.[1] The emission factor equation was

derived from regression analyses of 83 tests for PM10 on public and industrial paved 

roads. Airborne PM emissions were most closely correlated with vehicle weight and silt 

loading (the mass of material 75 microns or less per square meter of roadway). Inputs to 

the paved road dust emission factor equation were developed from California-specific 

roadway silt loading measurements [2,3,4,5]and average vehicle weight data measured by 

Midwest Research Institute (MRI).

[5]

This updates estimates California paved road dust 

emissions for 2008. Data from the ARB, air districts and transportation planning agencies 

were used to estimate county-specific vehicle miles traveled (VMT).

[6] California 

Department of Transportation (Caltrans) Highway Performance Monitoring System 

(HPMS) data were used to estimate the fraction of travel on each of the four road types in 

each county: freeway, major, collector, and local.

[7,8] Western Regional Climate Center 

precipitation data were used to estimate the number of days per year that each county 

received 0.01 inch or greater of precipitation.

[9]

OVERVIEW OF ESTIMATION METHODOLOGY

Particulate emissions less than 10 microns in diameter (PM10) from re-suspension of road 

surface material by vehicle travel on paved roads (entrained paved road dust) are 

computed using the emission factor equation in the Final Section of the U.S. EPA’s 

January 2011 AP-42, Fifth Edition, Volume 1, Chapter 13.2.1.[1]The methodology does 

not include directly emitted motor vehicle emissions (exhaust, brake or tire wear), nor 

TOG, CO, NOx, SOx, or PM exhaust emissions; these emissions are included in ARB’s
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motor vehicle emission inventory.

[10]

Emission estimates for dust from constructing new 

roads are provided in ARB’s Road Construction Dust methodology.

[11]

EMISSION ESTIMATION METHODOLOGY

The 2011 AP-42 emission factor equation used to estimate paved road dust emissions in 

California is provided below, followed by a description of the inputs to the equation:

[1]

E = [k(sL)

0.91

x (W)

1.02] x (1 – P/4N)

Where: 

E = the particulate emission factor in units of pounds of particulate matter per VMT

k = the U.S. EPA AP-42 particle size multiplier (PM10 = 0.0022 lb/VMT),[1]

sL = the roadway-specific silt loading in grams/square meter (g/m2),

[2,3,4,5]

W = the average weight of vehicles traveling the road (California statewide default 

 = 2.4 tons),

[5]

P = number of “wet” days, when at least one site per county received at least 0.01 inch 

 of precipitation during the annual averaging period,[9]and 

N = the number of days in the annual averaging period (default = 365)

PM2.5 (particulate matter less than 2.5 microns in diameter) and TSP (total suspended 

particulate matter) were derived from the calculated PM10 emissions using ARB’s 

speciation profile #471 for paved road dust (see Table 1, below).

[12,13,14,15,16]

Size 

fractions are based on paved road dust sampling conducted in California and on 

evaluations conducted by ARB and MRI.

[13,15,16,17]

TSP emissions are back-calculated by 

dividing computed PM10 emissions by the < PM10 size fraction: 

TSP = PM10/0.4572. PM2.5 emissions are calculated by multiplying computed PM10

emissions by the size fraction ratio for (< PM2.5)/(< PM10): 

PM2.5 = [PM10 x (0.0686/0.4572)].

Table 1. ARB Paved Road Dust Particulate Matter (PM) 

Speciation Profile #471 [12,13,14,15,16,17]

Particulate

Matter Size Fraction

PM10 < PM10 0.4572

PM2.5 < PM2.5 0.0686

 TSP > PM10 0.5428

Roadway Category Splits

The HPMS, a federally mandated inventory system and planning tool designed to assess 

the nation’s highway system, is used by State and Federal governments and local 

agencies to analyze the system's condition and performance. HPMS provides data on 

vehicle miles traveled (VMT) for 12 functional systems, based on mobility and access 

considerations defined by the Federal Highway Administration (FHWA).

[7,8]

To 

calculate county-specific travel fractions for each roadway type, ARB apportioned 2008

Caltrans HPMS paved road VMT to the four ARB roadway classifications (freeway, 
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major, collector and local), based on their anticipated usage, modes of usage, and silt 

loading potential.

[7]

Local data can be incorporated for regions that are able to provide 

more refined travel fraction data than are available through HPMS. Data for unspecified 

roads (canals, drainage ditches, etc.) are provided directly by air districts and counties. 

Table 2 shows how HPMS functional systems are distributed to ARB road categories and 

provides FWHA functional system characteristics.

Table 2. ARB Roadway Categories, Caltrans HPMS Functional Systems 

and FHWA Functional System Characteristics[2,7,8]

ARB Category HPMS Functional System FHWA Functional System Characteristics

Systems for Rural Areas (populations < 5,000)

Freeway Interstate

All designated routes of the Interstate System. 

Provides substantial interstate travel, highest overall 

travel speeds.

Major

Other Principal Arterial Non-interstate principal arterials

Minor Arterials

Provides substantial statewide travel, links cities 

and larger towns, links to interstates and intercounty service; relatively high travel speeds.

Collector Major Collector Primarily intra-county; shorter distances and more 

moderate travel speeds than arterials.

Local

Minor Collector

Collects traffic from local roads, services smaller 

communities, links locally important traffic 

generators with remote areas. 

Local Provides access to adjacent land over relatively 

short distances.

Systems for Urban Areas (populations > 5,000)

Freeway Interstate, Other Freeway 

and Expressway

Highest level of mobility, highest traffic volumes 

and travel speeds, controlled access routes. Serves 

longest trips and through-movement as well as 

access to major urban centers. Provides intra-area 

travel, intra-urban and inter-city bus routes. 

Integrates with major rural connections.

Major

Other Principal Arterial Provides service to major traffic movements, 

uncontrolled access to adjacent land.

Minor Arterial

Interconnects, augments urban principal arterial 

system, distributes travel to smaller geographic 

areas, may carry local bus routes. Serves trips of 

moderate length at somewhat lower mobility and 

speeds. Connects to rural collector roads.

Collector Collector

Provides land access, traffic circulation within 

residential neighborhoods, commercial and 

industrial areas. Connects to the arterial system.

Local Local

Provides direct access to abutting land and higher

order functional systems. Restricts throughmovement, generally contains no bus routes.
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Silt Loadings

ARB assigned silt loadings to four roadway types (freeway, major, collector, local), 

assuming that more highly traveled roadways with fewer entrance and exit points (limited 

access roadways such as freeways) have less silt loading compared to roadways with 

multiple access and exit points, and that roads with similar configurations and usage have 

similar silt loadings statewide. While ARB understands the limitations to this assumption, 

especially in computing localized emissions, our current strategy is to use the best 

available California roadway silt loading data to estimate regional entrained road dust 

emissions. Table 3, below, presents proposed statewide default silt loading values for the 

four ARB roadway categories, as well as the derivation of several district and county

specific silt loadings. Silt loadings for unspecified roads were provided directly by air 

districts and counties. A summary of the data used to develop the silt loadings may be 

found in Appendix A, Table 1. The basis for the proposed silt loading values is as 

follows:

Statewide Default Silt Loadings

 Freeway – U.S. EPA AP-42 default[1]

 Major and Collector roadways – geometric mean of 31 California-specific silt 

measurements of roads with high average daily traffic (ADT) conducted by 

MRI[2,5]and the University of California, Davis (UCD).

[2,3,4]

 Local roadways – mean of eleven California-specific silt measurements of roads 

with low ADT conducted by MRI.

[2,5]

District and County Specific Silt Loadings

 The San Joaquin Valley Air Pollution Control District (SJVAPCD) splits local 

roads into urban and rural classes and assigns separate silt loading values to each 

class. Local urban roads are assigned the statewide Local road default silt loading 

value. A higher silt loading value (derived from U.S. EPA AP-42 data) is assigned 

to local rural roads due to anticipated higher silt loading levels from agricultural 

activities.

[2]

 For Major, Collector and Local roads, the portion of Los Angeles County in the 

South Coast Air Quality Management District (SCAQMD) and all portions of 

Orange, Riverside and San Bernardino counties use silt loading values based on 

subsets of measurements collected in the SCAQMD and Riverside County.

[2,5]
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Table 3. California Statewide and Local Default Silt Loading Values

Roadway Category Silt Loading (sL) (g/m2) Source of sL Value

California Statewide Silt Loading Values

Freeway 0.02 U.S. EPA default value[1]

Major 0.032 Geometric mean of 31 California 

samples[2,3,4,5]

Collector 0.032 Geometric mean of 31 California 

samples[2,3,4,5]

Local 0.32 Average of 11 California BACM 

samples[5]

District and County Specific Silt Loading Values

District Specific - SJVAPCD/a

 Local Rural (PM10) 1.6 Average sL, AP-42 Local roads[1,2]

County Specific/b

 Major, Collector

 Los Angeles & Orange

 counties: Maj-Coll[LA&OR]

 Riverside & San Bernardino

 counties: Maj-Coll[RIV&SB]

Major-Collector Scaling Ratio

Maj-Coll[RIV&SB]/Maj-Coll[LA&OR]

 Local

 Los Angeles & Orange

 counties: Local[LA&OR]

 Riverside & San Bernardino

 counties: Local[RIV&SB]

0.013

0.08

(0.08/0.013) = 6.2

0.135

Local[LA&OR] x 6.2 = Local[RIV&SB]

0.135 x 6.2 = 0.84

0.013 = Mean of 3 of the 4 South 

Coast High ADT/c BACM/d sL

measurements[2,5]

0.08 = Mean of all South Coast 

Low ADT BACM sL

measurements[2,5]

6.2 is used below to scale 

sL Local[LA&OR] to sL Local[RIV&SB]

0.135 = Geometric mean of 11 CA

High ADT sL measurements[5]

Local[LA&OR] scaled using ratio of 

Maj-Coll[RIV&SB]/Maj-Coll[LA&OR]

[2,5]

a San Joaquin Valley Air Pollution Control District

b Silt loadings apply to the portion of Los Angeles County in the South Coast Air 

Quality Management District and all portions of Orange, Riverside, and San 

Bernardino counties

c ADT, Average Daily Traffic

d BACM, Best Available Control Measures

Vehicle Weight Estimates

The estimated statewide average vehicle weight is based on an informal traffic count 

conducted by MRI while performing California silt loading measurements.[2,5]The 

statewide default fleet vehicle weight is 2.4 tons; Table 9 contains fleet vehicle weights. 
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Activity Data: Vehicle Miles Traveled (VMT)

ARB used 2008 VMT data from EMFAC2011-SG to develop the paved road dust 

emissions inventory.

[6]

Tables 5 and 8 list 2008 VMT (millions of miles) by county and 

air basin; Table 8 also provides the 2008 HPMS county specific travel fractions used to 

distribute VMT to the roadway categories. Table footnotes provide source information 

for VMT and/or travel fraction data provided by local air districts or transportation 

planning agencies. 2007 VMT data from EMFAC2011-SG were used for the modeling 

inventory.

Paved Road PM Emissions Estimates

Tables 5 – 7 present uncontrolled paved road dust PM emissions, with the exception of 

SCAQMD Unspecified Roads, which reflect District controls. Table 5 presents PM10

paved road dust emissions for 2008, in tons/year, by paved road category within county 

and air basin. Tables 6 and 7, respectively, provide 2008 paved road dust emissions for 

PM2.5 and TSP. Table 9 shows emission factors (lbs/106 VMT) for PM10 and 2008 

roadway silt loadings (g/m2) by county within air basin. Emission factors for SCAQMD 

Unspecified Roads are uncontrolled.

Rainfall Adjustment

Table 10 shows the number of days per year that at least one site in each county, within 

air basin, received 0.01 inch or more of precipitation.

[9]

The data are based on average 

annual days of precipitation per month over the years of record. 

TEMPORAL ACTIVITY

Total annual entrained paved road dust emissions are allocated on a monthly basis. 

During the wet winter months, the relative contribution of paved road emissions is 

reduced compared to non-rainy months. Table 11 presents the temporal adjustments used 

to reflect rainfall patterns for each county, within air basin.

[9]

ASSUMPTIONS AND LIMITATIONS

1. The current U.S. EPA AP-42 emission factor assumes that road dust emissions are 

proportional to VMT, roadway silt loading, and average vehicle weight. 

2. The methodology assumes that roadway silt loading varies by road type, quickly 

reaches an equilibrium condition, and is adequately characterized by a roadwayspecific silt loading factor. Thus, the emission factor varies by the type of road. 

3. The Major, Collector and Local roadway silt loadings are based on a total of 42 silt 

loading measurements collected from 1995 to 1997 in the South Coast Air Basin, 

Coachella Valley, Bakersfield and Sacramento. This does not fully represent the 

variability in California silt loading. 

4. It is assumed that the U.S. EPA PM10 particle size multiplier (i.e., the ‘k’ factor in the 

AP-42 equation) reasonably represents the size distribution of California paved road 

dust. 
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5. ARB’s speciation profile for entrained paved road dust is based on six measurements 

collected in the San Joaquin Valley and in Imperial and Mono counties and may not 

fully reflect the variability of particle size distributions throughout California.

6. The average vehicle fleet weight is assumed to be 2.4 tons statewide.

7. HPMS VMT data by county for 2008 are assumed to accurately represent actual 

California roadway mileage and thus the travel fractions for each roadway type.

8. It is assumed that the average annual number of days of precipitation >0.01 inch 

remain constant for each county, within air basin.

9. It is assumed that the temporal profile based on county- and air basin-specific 

monthly rainfall provides appropriate adjustments to allocate unpaved road dust 

emissions on a monthly basis.

CHANGES IN THE METHODOLOGY

There were substantial changes in the paved road dust emission estimates for this update.

These include:

1. Incorporation of the U.S. EPA paved road emission factor equation from the Final 

Section of the Fifth Edition of U.S. EPA's AP-42 document (January 2011, Chapter

13.2.1).

[1] Newly incorporated are:

a. A revised PM10 emission factor equation based on regression analyses of 83 tests 

of emissions from public and industrial paved roads. 

b. The emissions testing included recent vintage light duty vehicles. The previous 

update was based on emissions testing of 1980’s fleet vehicles.

c. Elimination of brake wear, tire wear and exhaust (B/T/E) emissions from the 

emission factor equation. The previous update included B/T/E emissions, which 

represented double-counting with the mobile inventory. For the new emission 

factor equation, B/T/E emissions were subtracted from total emissions prior to 

running the regressions. 

d. New exponents for the vehicle fleet weight and silt loading terms and revised 

PM10 particle size multiplier (“k” term, 0.0022 lbs PM10/VMT)

e. A precipitation adjustment factor (1-P/4N) to reflect the dust suppression effects 

of days with > 0.01 inch precipitation.

2. Estimates of paved road dust PM2.5 emissions are presented for the first time, 

calculated using ARB’s particle speciation profile #471.[12,13,14,15,16,17]In 2006, ARB 

updated the PM2.5/PM10 particle size fraction from 16.9% to 15%.[15]

3. Incorporation of a revised statewide silt loading value of 0.032 g/m2for the Major 

and Collector roadway categories, based on the geometric mean of 31 silt loading 

measurements collected between 1995-1997 on roadways with high ADT in the 

Coachella Valley, Bakersfield, Riverside, Sacramento and the South Coast air 

basin.

[2,3,4,5]

For Major, Collector and Local roads, the portion of Los Angeles County 

in the SCAQMD and all portions of Orange, Riverside and San Bernardino counties 

use silt loading values based on subsets of the measurements in the SCAQMD and 

Riverside.

[2,5]

SJVAPCD separates Local roads into local urban and local rural roads

and uses the statewide default silt loading value for local urban roads. They assume 

that agricultural activities generate a higher silt loading potential for local rural roads
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and assign a value based on an average of U.S. EPA AP-42 silt loading values for 

Local roads.

[1,2]

4. Update of VMT data to 2008 levels based on EMFAC2011 reports of annualized 

VMT per average weekday for the year 2008.

[6]

5. Update of the fractions of vehicle miles traveled on Freeway, Major, Collector, and 

Local roads to reflect 2008 Caltrans HPMS data.

[7,8]

6. Incorporating temporal adjustments to reflect county-specific rainfall patterns, within

air basin.[9]

The above changes reduced the statewide PM10 paved road emissions by about 58% from 

estimates provided in the 2009 ARB Almanac, which is based on 1997 emission 

inventory estimates, grown to 2008.[2,18,19]

COMMENTS AND RECOMMENDATIONS

Research is ongoing to better understand and quantify paved road dust emissions, with 

recent studies employing mobile monitoring technologies.

[20,21] When available, the 

studies will be evaluated and incorporated as appropriate into this methodology. Also, 

effort is needed to better account for the variability in dust emissions based on population 

density, adjacent land uses, and geographic location.

Silt Loading. This methodology assumes that silt loading values vary by roadway type. 

Additional research is needed to fully characterize the relationship between roadway type 

and silt loading values. Also, additional county-specific silt loading measurements are 

needed to more accurately reflect the variability of silt loading throughout California. 

Fleet Vehicle Weight. Based on a 1995 informal traffic count conducted by MRI, the 

average fleet vehicle weight is assumed to be 2.4 tons.

[2,5]

This value should be reevaluated to ensure accurate average vehicle fleet weights are used to estimate dust 

emissions. Since the vehicle distribution among counties may vary, the evaluation should 

consider county-specific average weights. 

Calculating Paved Road PM2.5. The Final Section of the U. S. EPA’s January 2011 AP-42 

for paved roads assigns a particle size fraction of 25% to PM2.5 (PM2.5 = PM10 x 25%).

[1]

This fraction is based on test conditions that include heavy vehicles traveling at very slow 

speeds (less than 5 mph) at corn processing facilities in the Midwest, and are not 

representative of typical travel on public and industrial paved roads in California. The

January 2011 PM2.5 fraction is 60% greater than the PM2.5 particle size fraction of 15%

that was used in the previous version of AP-42 (see Reference 1, Chapter 13.2.1; 

Background Documentation, Section 2.2.5).

For this update, paved road PM2.5 is calculated using ARB speciation profile #471, which 

was derived from testing conducted in the San Joaquin Valley and in Imperial and Mono 

counties.

[12,13,14] ARB updated their PM2.5 fugitive dust profiles in 2006, after a review of 

recent Western Regional Air Partnership (WRAP) studies and ARB’s emission inventory 

vs. ambient air quality measurement data indicated that PM2.5 from these sources was 
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overestimated in California.[15,16,17,22]The paved road PM2.5/PM10 fraction was updated 

from 16.9% to 15% to more accurately reflect measured PM2.5 emissions.[15] Since ARB 

uses this speciation profile for emissions modeling, using this approach to calculate

paved road PM2.5 emissions will also provide consistency between emission estimates for 

planning and inventory.

Temporal Profiles. The previous update applied a single temporal profile statewide.[2] In 

2001, under the sponsorship of the Central California Ozone Study (CCOS), researchers 

developed temporal profiles for a number of area and off-road emission sources, 

including paved roads.[23,24] On a statewide basis, the temporal profile proposed by the 

CCOS study allocated an average of up to 75% of annual emissions to the summer 

months. However, full documentation was not provided for the derivation of the paved 

road temporal profiles and ARB could not recreate the results. Based on newer research

that shows minimal seasonal variation for paved road dust emissions, ARB developed 

relatively flat monthly allocations of annual paved road dust emissions for this 

update.[25,26,27]The new temporal profiles (Table 11) are calculated using county and air 

basin specific records for monthly days of rain (Table 10).[9]

SAMPLE CALCULATIONS

Sample emissions calculations are provided below in Table 4. Steps 1 - 5 summarize the 

data computations necessary to estimate the annual tons of paved road dust PM10

emissions in Santa Cruz County. Steps 6 and 7, respectively, describe how to calculate 

annual tons of TSP and PM2.5 from PM10. The following steps are performed:

Step 1: Silt Loadings. Locate the appropriate ARB default silt loadings in Table 3 or use 

local silt loadings if better data are available. (Silt loadings are presented by 

county and air basin in Table 8.)

Step 2: Emission Factor. Using the silt loadings from Step 1 and the AP-42 emission factor 

equation shown previously, compute the emission factor for each road type. For Santa 

Cruz County, a default average vehicle weight of 2.4 tons and a k factor of 

0.0022 lb PM10/VMT from AP-42 are used. 

Step 3: Using Table 8 data, fill in the road-specific travel fraction data. 

Step 4: Multiply the county EMFAC2011 VMT for 2008 provided in Table 8 by the 

travel fraction values from Step 3 to compute the VMT traveled on each roadway 

type.

 Total VMT x Travel Fraction = Road VMT

Step 5: Multiply each emission factor from Step 2 by the VMT data from Step 4 to 

compute pounds of PM10 emissions for each road type. 

 Road EF x Road VMT = Road Emissions

 Divide the computed values by 2000 lbs/ton to calculate the annual tons of 

PM10/year from paved road dust.

 Tons/year PM10 = Road Emissions/2000

Step 6: Because the ARB’s database system maintains particulate emissions as 

TSP, PM10 emissions must next be converted to TSP emissions. For California 

paved road dust, it is estimated that 45.72% of TSP is PM10, therefore, dividing 
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the PM10 value by 0.4572 produces the correct TSP emissions.

 Tons/year TSP = (Tons/year PM10)/(0.4572)

Step 7: Calculate PM2.5 emissions from PM10 emissions using ARB’s speciation profile 

#471, which provides a PM2.5 particle size fraction of 0.0686:

 Tons/year PM2.5 = (Tons/year PM10)/(0.4572) x 0.0686

Table 4. Estimating Paved Road Dust Emissions in Santa Cruz County/a

ARB Roadway Category

Steps Factors Freeway Major Collector Local Totals

1 Silt Loading (g/m2) 0.02 0.032 0.032 0.32

2 Emission Factor PM10

(lbs PM10/million VMT)

146.0 223.95 223.95 1820.3

3 Travel Fraction 0.271 0.476 0.187 0.066 1

4 VMT, 2008, million/yr 687.5 1207.6 474.4 167.4 2,537

5 PM10 Emissions, tons/yr 50.2 135.2 53.1 152.4 391

6 TSP Emissions, tons/yr 109.8 295.8 116.2 333.2 855

7 PM2.5 Emissions, tons/yr 7.5 20.3 8.0 22.9 59

a The sample calculations use input data from Tables 5-7, which are rounded from raw data. 

Thus, calculated values in Table 4 may differ slightly from values shown in Tables 5-7.

ADDITIONAL CODES

SOURCE CATEGORY GROWTH AND CONTROL CODES

Various

SOURCE CATEGORY CODE POLLUTANT SPECIATION PROFILES

For All: PM10 = 471, VOC = not applicable

SOURCE CATEGORY CODE REACTIVITY FACTORS

Not Applicable

REFERENCES

1. U.S. Environmental Protection Agency. Compilation of Air Pollutant Emissions 

Factors, AP-42, Section 13.2.1, Paved Roads. January 2011.

http://www.epa.gov/ttn/chief/ap42/ch13/index.html

2. Gaffney, P. Entrained Dust from Paved Road Travel, Emission Estimation 

Methodology Background Document. California Air Resources Board. July 1997.

http://www.arb.ca.gov/ei/areasrc/arbmiscprocpaverddstbkgrnd.pdf

3. Ashbaugh, L., Flocchini, R., et al. Final Report, Traffic Generated PM10 “Hot Spots”. 

Prepared for Caltrans by the Air Quality Group, Crocker Nuclear Laboratory, 

University of California, Davis, Contract Number 53V606 A2, August, 1996. 

http://aqp.engr.ucdavis.edu/Documents/1996-Ashbaugh-UCDCaltrans.pdf

4. Ashbaugh, L., Flocchini, R., et al. Final Report, Wintertime Traffic Generated PM10

“Hot Spots”. Prepared for Caltrans by the Air Quality Group, Crocker Nuclear 

Laboratory, University of California, Davis, Contract Number 43X878, September 3, 

1998. http://aqp.engr.ucdavis.edu/Documents/pm10_hotspot_Sunrise.pdf
MISCELLANEOUS PROCESS METHODOLOGY 7.9

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5. Muleski, G. Improvement of Specific Emission Factors (BACM Project No. 1), Final 

Report. Midwest Research Institute, March 29, 1996.

6. EMFAC2011-SG (September 12, 2011). 2007 and 2008 Default Statewide Vehicle 

Miles Traveled (VMT) by County/Air Basin, per Average Weekday.

7. California Department of Transportation. Highway Performance Monitoring System 

(HPMS) Vehicle Miles Traveled (VMT) per Day by County and Roadway Functional 

Classification for 2008. Excel file provided by Brian Domsic, June 10, 2009.

8. U.S. Department of Transportation, Federal Highway Administration, FHWA 

Functional Classification Guidelines. April 2000. 

http://www.fhwa.dot.gov/planning/fcsec2_1.htm#ad

9. Western Regional Climate Center, Average Number of Days per Month with Rainfall 

of 0.01 Inch or Greater, by County/Air Basin, for Years of Record. 

http://www.wrcc.dri.edu/ Accessed May 8, 2009

10. California Air Resources Board, EMission FACtors Model, EMFAC 2007 v2.3 

Release, November 2006. http://www.arb.ca.gov/msei/onroad/latest_version.htm

11. Gaffney, P. Emission Estimation Methodology Section 7.8, Road Construction Dust,

California Air Resources Board. August 1997. 

http://www.arb.ca.gov/ei/areasrc/fullpdf/full7-8.pdf

12. California Air Resources Board, Speciation Profiles Used in ARB Modeling. 

http://www.arb.ca.gov/ei/speciate/dnldoptvv10001.php#specprof

13. Houck, J.E., Chow, J.C., Watson, J.G., et al. Determination of Particle Size 

Distribution and Chemical Composition of Particulate Matter from Selected Sources 

in California, Final Report. Desert Research Institute & OMNI Environmental. 

Prepared for California Air Resources Board. Agreement No. A6-175-32. June 30, 

1989. http://www.arb.ca.gov/ei/speciate/r01t20/rf20doc/refnum20.htm

14. Chow, J.C., Watson, J.G., Ashbaugh, L.L., Magliano, K.L. 2003. Similarities and 

differences in PM10 chemical source profiles for geological dust from the San Joaquin 

Valley, California. Atmospheric Environment 37:1317-1340. 2003.

http://www.arb.ca.gov/ei/speciate/r01t20/rf13doc/Ref%2013%20-

%20Chowetal2003AESJVFugDustProfiles.pdf

15. Gaffney, P. Updating the ARB PM2.5 Size Speciation Profiles for Fugitive Dust 

Sources. California Air Resources Board. August 2006.

16. Countess Environmental. Western Regional Air Partnership’s (WRAP) Fugitive Dust 

Handbook, prepared for the Western Governors’ Association, WGA Contract No. 

30204-111. September 7, 2006.

http://www.wrapair.org/forums/dejf/fdh/content/FDHandbook_Rev_06.pdf

17. Cowherd, C. Background Document for Revisions to Fine Fraction Ratios Used for 

AP-42 Fugitive Dust Emission Factors. Prepared by Midwest Research Institute for 

Western Governors’ Association, Western Regional Air Partnership. MRI Project 

No. 110397. Finalized Nov. 1, 2006

http://www.epa.gov/ttnchie1/ap42/ch13/bgdocs/b13s02.pdf
MISCELLANEOUS PROCESS METHODOLOGY 7.9

Entrained Paved Road Travel, Paved Road Dust

Page 12 of 27

18. Gaffney, P. Emission Estimation Methodology Section 7.9, Entrained Paved Road 

Dust. California Air Resources Board. July 1997. 

19. California Air Resources Board, 2009 Almanac Emission Projection Data for 2008.

http://www.arb.ca.gov/app/emsinv/emssumcat.php

20. Cowherd, C., Technical Support Document for Mobile Monitoring Technologies. 

Midwest Research Institute. Prepared for Rodney Langston and Russell S. Merle, Jr., 

Clark County Department of Air Quality and Environmental Management, Las 

Vegas, NV. Jan. 2009.

http://www.epa.gov/ttnchie1/ap42/ch13/related/Mobile_Monitoring_TSD_010909.pdf

21. Langston, R., Merle, R. S., Jr. Clark County (Nevada) Paved Road Dust Emission 

Studies in Support of Mobile Monitoring Technologies. Clark County Department of 

Air Quality and Environmental Management (DAQEM). December 22, 2008. 

http://www.epa.gov/ttnchie1/ap42/ch13/related/Final_Test_Report.pdf

22. Cowherd, C., Donaldson, J. Analysis of the Fine Fraction of Particulate Matter in 

Fugitive Dust, Final Report. October 12, 2005. Prepared by Midwest Research 

Institute for the Western Governors’ Association, Western Regional Air Partnership. 

MRI Project No. 110397. 

http://www.wrapair.org/forums/dejf/documents/fffd/Final_Fine_Fraction_Dust_Report.pdf

23. California Air Resources Board. Central California Air Quality Studies. 

http://www.arb.ca.gov/airways/

24. Sonoma Technology, Inc. Revised Temporal Allocation Factors for Area and OffRoad Emissions Sources. Technical Memorandum of Sept. 26, 2001, STI Ref. No. 

900201. http://www.arb.ca.gov/ei/areasrc/temporalprofile010926.pdf

25. Mid-Atlantic Regional Air Management Association, Inc. (MARAMA). Paved Road 

Area Source Category Calculation Methodology Sheet. December 20, 2004. 

http://www.marama.org/visibility/Calculation_Sheets/index.htm

26. Kuhns, H., Etyemezian, V., Green, M., et al. Vehicle-based road dust emission 

measurement – Part II: Effect of precipitation, wintertime road sanding, and street 

sweepers on inferred PM10 emission potentials from paved and unpaved roads. 

Atmospheric Environment Vol. 37, Issue 32 (2003) 4573-4582. 

http://www.sciencedirect.com/science/article/pii/S1352231003005296

27. ENVIRON International Corp. WRAP Mobile Source Emission Inventories Update, 

Final Report. Prepared for the Western Governors’ Association. May 2006.

http://www.swcleanair.org/gorgedata/WRAP_MobileSourceEI.pdf

PREPARED BY

Janet Spencer

July 2013
Page 13 of 27

1 2008 VMT from EMFAC2011-SG (Sept. 12, 2011) except for VMT on sand and gravel processing facility roads (see footnote 4).

2 SJU District (San Joaquin Valley Air Pollution Control District): Local emissions include only Local Urban roadways.

3 The SJU District splits local roads into urban and rural classes, and uses separate silt loading values. Due to anticipated higher 

silt loading levels, a higher silt loading value derived from AP-42 data is used in computing emissions for local rural roads

(Rural Streets, EIC 640-643-5400-0000).

4 SC District (South Coast Air Quality Management District, SCAQMD) data, controlled emissions from paved roads at sand and 

gravel processing facilities (Unspecified Paved Roads, EIC 640-636-5400-0000). 

5 Sacramento Area Council of Governments (SACOG) provided Sacramento County 2008 travel fractions.

TABLE 5

2008 Entrained Paved Road Dust Emissions for PM10

EMFAC2011

VMT for 2008 (1) 2008 Paved Road Dust PM10 Emissions, Tons/Year

Air 

Basin County District

(million VMT

per year) Freeway Major Collector

Local, Local 

Urban (2)

Local Rural (3), 

Sand/Gravel 

Proc. (4) Total

GB Alpine GBU 15 0.00 1.31 0.20 1.47 3

Inyo GBU 255 0.04 21.78 4.58 23.58 50

Mono GBU 144 0.00 12.74 1.40 18.53 33

LC Lake LAK 622 0.00 42.34 19.29 63.62 125

LT El Dorado ED 270 3.43 17.27 3.94 30.39 55

Placer PLA 127 3.76 5.38 1.59 11.19 22

MD Kern KER 1,448 29.18 93.81 13.62 120.15 257

Los Angeles AV 4,501 153.30 229.27 28.01 214.43 625

Riverside MOJ 368 13.30 32.69 12.33 52.80 111

Riverside SC 422 15.26 37.51 14.15 60.57 127

San Bernardino MOJ 8,702 342.80 784.91 159.92 1,322.06 2,610

MC Amador AMA 402 0.00 34.38 6.28 35.73 76

Calaveras CAL 511 0.00 39.21 10.61 58.21 108

El Dorado ED 1,603 20.37 102.54 23.37 180.42 327

Mariposa MPA 193 0.00 10.54 1.61 76.72 89

Nevada NSI 1,023 32.19 29.55 18.93 123.92 205

Placer PLA 547 16.21 23.23 6.87 48.26 95

Plumas NSI 213 0.00 12.29 6.46 40.20 59

Sierra NSI 36 0.36 1.71 0.60 8.73 11

Tuolumne TUO 561 0.00 36.58 15.46 87.39 139

NCC Monterey MBU 4,411 53.18 284.54 81.35 406.55 826

San Benito MBU 734 0.00 70.84 6.83 43.39 121

Santa Cruz MBU 2,537 50.18 135.12 53.23 152.76 391

NC Del Norte NCU 221 0.00 15.69 5.44 22.50 44

Humboldt NCU 1,263 19.65 67.43 23.76 117.16 228

Mendocino MEN 978 4.29 63.22 23.31 101.66 192

Sonoma NS 673 12.59 35.16 13.84 52.64 114

Trinity NCU 159 0.00 12.49 1.44 29.34 43

NEP Lassen LAS 273 0.00 18.02 7.85 39.16 65

Modoc MOD 86 0.00 4.31 2.13 24.93 31

Siskiyou SIS 569 18.40 13.96 7.55 101.89 142

SV Butte BUT 2,038 11.85 127.26 54.85 229.59 424

Colusa COL 241 10.76 4.53 2.09 32.44 50

Glenn GLE 300 11.85 7.02 4.07 35.21 58

Placer PLA 2,985 88.89 127.39 37.68 264.68 519

Sacramento (5) SAC 12,914 444.62 565.73 109.51 789.66 1,910

Shasta SHA 1,711 51.70 75.82 17.02 138.98 284

Solano YS 2,066 95.09 58.29 14.10 116.26 284

Sutter FR 758 4.83 52.93 10.83 106.48 175

Tehama TEH 733 26.24 21.57 12.11 63.39 123

Yolo YS 2,063 84.89 58.57 20.02 189.65 353

Yuba FR 717 8.65 40.48 17.72 72.61 139

SS Imperial IMP 2,383 49.34 125.59 46.43 239.78 461

Riverside SC 4,689 169.34 416.27 157.01 672.28 1,415

SD San Diego SD 29,665 1,216.94 1,075.73 270.70 1,329.48 3,893

TABLE 5 CONTINUES ON NEXT PAGE
Page 14 of 27

1 2008 VMT from EMFAC2011-SG (Sept. 12, 2011) except for VMT on sand and gravel processing facility roads (see footnote 4).

2 SJU District (San Joaquin Valley Air Pollution Control District): Local emissions include only Local Urban roadways.

3 The SJU District splits local roads into urban and rural classes, and uses separate silt loading values. Due to anticipated higher 

silt loading levels, a higher silt loading value derived from AP-42 data is used in computing emissions for local rural roads

(Rural Streets, EIC 640-643-5400-0000).

4 SC District (South Coast Air Quality Management District, SCAQMD) data, controlled emissions from paved roads at sand and 

gravel processing facilities (Unspecified Paved Roads, EIC 640-636-5400-0000). 

5 Sacramento Area Council of Governments (SACOG) provided Sacramento County 2008 travel fractions.

TABLE 5, continued

2008 Entrained Paved Road Dust Emissions for PM10

EMFAC2011

VMT for 2008

(1)

2008 Paved Road Dust PM10 Emissions, Tons/Year

Air 

Basin County District

(million VMT

per year) Freeway Major Collector

Local, Local 

Urban (2)

Local Rural (3), 

Sand/Gravel 

Proc. (4) Total

SF Alameda BA 14,397 596.80 512.58 103.58 692.75 1,906

Contra Costa BA 10,082 381.97 378.61 75.20 758.70 1,594

Marin BA 2,376 86.15 77.13 38.78 145.09 347

Napa BA 1,863 24.43 109.11 42.43 155.31 331

San Francisco BA 4,922 129.18 285.94 37.28 235.74 688

San Mateo BA 7,543 311.25 270.72 53.05 378.15 1,013

Santa Clara BA 15,374 487.36 773.45 92.29 889.86 2,243

Solano BA 2,840 131.08 80.35 19.44 160.27 391

Sonoma BA 3,988 74.99 209.34 82.41 313.43 680

SJV Fresno SJU 8,024 173.86 389.28 114.73 512.97 2,726.19 3,917

(2,3) Kern SJU 6,890 137.54 442.19 64.19 141.94 1,835.93 2,622

Kings SJU 1,398 27.41 80.22 23.05 33.62 354.64 519

Madera SJU 1,844 19.03 136.21 20.97 119.56 300.31 596

Merced SJU 2,949 53.62 177.50 42.05 142.95 614.93 1,031

San Joaquin SJU 5,808 194.88 229.79 76.62 97.82 1,324.87 1,924

Stanislaus SJU 4,208 93.13 178.53 108.70 79.15 1,258.68 1,718

Tulare SJU 3,479 39.35 216.20 68.30 230.22 819.64 1,374

SCC San Luis Obispo SLO 2,569 40.15 178.82 25.27 217.71 462

Santa Barbara SB 4,398 97.29 252.01 63.24 281.58 694

Ventura VEN 7,087 196.07 380.97 66.84 522.77 1,167

SC (4) Los Angeles SC 76,645 2,592.43 1,708.02 208.64 1,708.98 264.20 6,482

Orange SC 26,752 964.95 581.18 36.84 695.06 78.06 2,356

Riverside SC 13,114 467.98 1,150.42 433.91 1,857.91 138.10 4,048

San Bernardino SC 13,544 526.80 1,206.22 245.76 2,031.70 120.09 4,131

Statewide Totals 339,224 10,911 15,052 3,494 20,354 9,836 59,646
Page 15 of 27

1 PM2.5 emissions are calculated from entrained paved road emissions for PM10 using ARB’s speciation profile 471: 

PM2.5 = (PM10/0.4572) x 0.0686. See http://www.arb.ca.gov/ei/speciate/dnldopt.htm#specprof

2 SJU District (San Joaquin Valley Air Pollution Control District): Local emissions include only Local Urban roadways.

3 The SJU District splits local roads into urban and rural classes, and uses separate silt loading values. Due to anticipated higher 

silt loading levels, a higher silt loading value derived from AP-42 data is used in computing emissions for local rural roads 

(Rural Streets, EIC 640-643-5400-0000).

4 SC District (South Coast Air Quality Management District, SCAQMD) data, controlled emissions from paved roads at sand and 

gravel processing facilities (Unspecified Paved Roads, EIC 640-636-5400-0000).

5 Sacramento Area Council of Governments (SACOG) provided Sacramento County 2008 travel fractions.

TABLE 6

2008 Entrained Paved Road Dust Emissions for PM2.5

2008 Paved Road Dust PM2.5 Emissions, Tons/Year (1)

Air 

Basin County District Freeway Major Collector

Local, Local 

Urban (2)

Local Rural (3), 

Sand/Gravel Proc. (4) Total

GB Alpine GBU 0.0 0.2 0.0 0.2 0

Inyo GBU 0.0 3.3 0.7 3.5 7

Mono GBU 0.0 1.9 0.2 2.8 5

LC Lake LAK 0.0 6.4 2.9 9.5 19

LT El Dorado ED 0.5 2.6 0.6 4.6 8

Placer PLA 0.6 0.8 0.2 1.7 3

MD Kern KER 4.4 14.1 2.0 18.0 39

Los Angeles AV 23.0 34.4 4.2 32.2 94

Riverside MOJ 2.0 4.9 1.8 7.9 17

Riverside SC 2.3 5.6 2.1 9.1 19

San Bernardino MOJ 51.4 117.7 24.0 198.3 391

MC Amador AMA 0.0 5.2 0.9 5.4 11

Calaveras CAL 0.0 5.9 1.6 8.7 16

El Dorado ED 3.1 15.4 3.5 27.1 49

Mariposa MPA 0.0 1.6 0.2 11.5 13

Nevada NSI 4.8 4.4 2.8 18.6 31

Placer PLA 2.4 3.5 1.0 7.2 14

Plumas NSI 0.0 1.8 1.0 6.0 9

Sierra NSI 0.1 0.3 0.1 1.3 2

Tuolumne TUO 0.0 5.5 2.3 13.1 21

NCC Monterey MBU 8.0 42.7 12.2 61.0 124

San Benito MBU 0.0 10.6 1.0 6.5 18

Santa Cruz MBU 7.5 20.3 8.0 22.9 59

NC Del Norte NCU 0.0 2.4 0.8 3.4 7

Humboldt NCU 2.9 10.1 3.6 17.6 34

Mendocino MEN 0.6 9.5 3.5 15.2 29

Sonoma NS 1.9 5.3 2.1 7.9 17

Trinity NCU 0.0 1.9 0.2 4.4 6

NEP Lassen LAS 0.0 2.7 1.2 5.9 10

Modoc MOD 0.0 0.6 0.3 3.7 5

Siskiyou SIS 2.8 2.1 1.1 15.3 21

SV Butte BUT 1.8 19.1 8.2 34.4 64

Colusa COL 1.6 0.7 0.3 4.9 7

Glenn GLE 1.8 1.1 0.6 5.3 9

Placer PLA 13.3 19.1 5.7 39.7 78

Sacramento (5) SAC 66.7 84.9 16.4 118.4 286

Shasta SHA 7.8 11.4 2.6 20.8 43

Solano YS 14.3 8.7 2.1 17.4 43

Sutter FR 0.7 7.9 1.6 16.0 26

Tehama TEH 3.9 3.2 1.8 9.5 18

Yolo YS 12.7 8.8 3.0 28.4 53

Yuba FR 1.3 6.1 2.7 10.9 21

SS Imperial IMP 7.4 18.8 7.0 36.0 69

Riverside SC 25.4 62.4 23.6 100.8 212

SD San Diego SD 182.5 161.4 40.6 199.4 584

TABLE 6 CONTINUES ON NEXT PAGE
Page 16 of 27

1 PM2.5 emissions are calculated from entrained paved road emissions for PM10 using ARB’s speciation profile 471: 

PM2.5 = (PM10/0.4572) x 0.0686. See http://www.arb.ca.gov/ei/speciate/dnldopt.htm#specprof

2 SJU District (San Joaquin Valley Air Pollution Control District): Local emissions include only Local Urban roadways.

3 The SJU District splits local roads into urban and rural classes, and uses separate silt loading values. Due to anticipated higher 

silt loading levels, a higher silt loading value derived from AP-42 data is used in computing emissions for local rural roads 

(Rural Streets, EIC 640-643-5400-0000).

4 SC District (South Coast Air Quality Management District, SCAQMD) data, controlled emissions from paved roads at sand and 

gravel processing facilities (Unspecified Paved Roads, EIC 640-636-5400-0000).

5 Sacramento Area Council of Governments (SACOG) provided Sacramento County 2008 travel fractions.

TABLE 6, continued

2008 Entrained Paved Road Dust Emissions for PM2.5

2008 Paved Road Dust PM2.5 Emissions, Tons/Year (1)

Air 

Basin County District Freeway Major Collector

Local, Local 

Urban (2) 

Local Rural (3), 

Sand/Gravel Proc. (4) Total

SF Alameda BA 89.5 76.9 15.5 103.9 286

Contra Costa BA 57.3 56.8 11.3 113.8 239

Marin BA 12.9 11.6 5.8 21.8 52

Napa BA 3.7 16.4 6.4 23.3 50

San Francisco BA 19.4 42.9 5.6 35.4 103

San Mateo BA 46.7 40.6 8.0 56.7 152

Santa Clara BA 73.1 116.0 13.8 133.5 336

Solano BA 19.7 12.1 2.9 24.0 59

Sonoma BA 11.2 31.4 12.4 47.0 102

SJV Fresno SJU 26.1 58.4 17.2 76.9 408.9 588

(2,3) Kern SJU 20.6 66.3 9.6 21.3 275.4 393

Kings SJU 4.1 12.0 3.5 5.0 53.2 78

Madera SJU 2.9 20.4 3.1 17.9 45.0 89

Merced SJU 8.0 26.6 6.3 21.4 92.2 155

San Joaquin SJU 29.2 34.5 11.5 14.7 198.7 289

Stanislaus SJU 14.0 26.8 16.3 11.9 188.8 258

Tulare SJU 5.9 32.4 10.2 34.5 122.9 206

SCC San Luis Obispo SLO 6.0 26.8 3.8 32.7 69

Santa Barbara SB 14.6 37.8 9.5 42.2 104

Ventura VEN 29.4 57.1 10.0 78.4 175

SC Los Angeles SC 388.9 256.2 31.3 256.3 39.6 972

(4) Orange SC 144.7 87.2 5.5 104.3 11.7 353

Riverside SC 70.2 172.6 65.1 278.7 20.7 607

San Bernardino SC 79.0 180.9 36.9 304.8 18.0 620

Statewide Totals 1,637 2,258 524 3,053 1,475 8,947
Page 17 of 27

1 TSP emissions are calculated from entrained paved road emissions for PM10 using ARB’s speciation profile 471: 

TSP = (PM10/0.4572). See http://www.arb.ca.gov/ei/speciate/dnldopt.htm#specprof

2 SJU District (San Joaquin Valley Air Pollution Control District): Local emissions include only Local Urban roadways.

3 The SJU District splits local roads into urban and rural classes, and uses separate silt loading values. Due to anticipated 

higher silt loading levels, a higher silt loading value derived from AP-42 data is used in computing emissions for local rural 

roads (Rural Streets, EIC 640-643-5400-0000).

4 SC District (South Coast Air Quality Management District, SCAQMD) data, controlled emissions from paved roads at sand 

and gravel processing facilities (Unspecified Paved Roads, EIC 640-636-5400-0000). 

5 Sacramento Area Council of Governments (SACOG) provided Sacramento County 2008 travel fractions.

TABLE 7

2008 Entrained Paved Road Dust Emissions for Total Suspended Particulates (TSP, Tons/Year)

2008 Paved Road Dust TSP Emissions, Tons/Year (1)

Air

Basin County District Freeway Major Collector

Local, Local 

Urban (2)

Local Rural (3), 

Sand/Gravel Proc (4) Total

GB Alpine GBU 0.0 2.9 0.4 3.2 7

Inyo GBU 0.1 47.6 10.0 51.6 109

Mono GBU 0.0 27.9 3.1 40.5 71

LC Lake LAK 0.0 92.6 42.2 139.1 274

LT El Dorado ED 7.5 37.8 8.6 66.5 120

Placer PLA 8.2 11.8 3.5 24.5 48

MD Kern KER 63.8 205.2 29.8 262.8 562

Los Angeles AV 335.3 501.5 61.3 469.0 1,367

Riverside MOJ 29.1 71.5 27.0 115.5 243

Riverside SC 33.4 82.0 30.9 132.5 279

San Bernardino MOJ 749.8 1,716.8 349.8 2,891.6 5,708

MC Amador AMA 0.0 75.2 13.7 78.1 167

Calaveras CAL 0.0 85.8 23.2 127.3 236

El Dorado ED 44.6 224.3 51.1 394.6 715

Mariposa MPA 0.0 23.0 3.5 167.8 194

Nevada NSI 70.4 64.6 41.4 271.0 447

Placer PLA 35.4 50.8 15.0 105.5 207

Plumas NSI 0.0 26.9 14.1 87.9 129

Sierra NSI 0.8 3.8 1.3 19.1 25

Tuolumne TUO 0.0 80.0 33.8 191.1 305

NCC Monterey MBU 116.3 622.4 177.9 889.2 1,806

San Benito MBU 0.0 154.9 14.9 94.9 265

Santa Cruz MBU 109.8 295.5 116.4 334.1 856

NC Del Norte NCU 0.0 34.3 11.9 49.2 95

Humboldt NCU 43.0 147.5 52.0 256.3 499

Mendocino MEN 9.4 138.3 51.0 222.3 421

Sonoma NS 27.5 76.9 30.3 115.1 250

Trinity NCU 0.0 27.3 3.2 64.2 95

NEP Lassen LAS 0.0 39.4 17.2 85.7 142

Modoc MOD 0.0 9.4 4.7 54.5 69

Siskiyou SIS 40.2 30.5 16.5 222.9 310

SV Butte BUT 25.9 278.4 120.0 502.2 926

Colusa COL 23.5 9.9 4.6 71.0 109

Glenn GLE 25.9 15.4 8.9 77.0 127

Placer PLA 194.4 278.6 82.4 578.9 1,134

Sacramento (5) SAC 972.5 1,237.4 239.5 1,727.2 4,177

Shasta SHA 113.1 165.8 37.2 304.0 620

Solano YS 208.0 127.5 30.9 254.3 621

Sutter FR 10.6 115.8 23.7 232.9 383

Tehama TEH 57.4 47.2 26.5 138.7 270

Yolo YS 185.7 128.1 43.8 414.8 772

Yuba FR 18.9 88.5 38.8 158.8 305

SS Imperial IMP 107.9 274.7 101.6 524.4 1,009

Riverside SC 370.4 910.5 343.4 1,470.4 3,095

SD San Diego SD 2,661.7 2,352.9 592.1 2,907.9 8,515

TABLE 7 CONTINUES ON NEXT PAGE
Page 18 of 27

1 TSP emissions are calculated from entrained paved road emissions for PM10 using ARB’s speciation profile 471: 

TSP = (PM10/0.4572). See http://www.arb.ca.gov/ei/speciate/dnldopt.htm#specprof

2 SJU District (San Joaquin Valley Air Pollution Control District): Local emissions include only Local Urban roadways.

3 The SJU District splits local roads into urban and rural classes, and uses separate silt loading values. Due to anticipated 

higher silt loading levels, a higher silt loading value derived from AP-42 data is used in computing emissions for local rural 

roads (Rural Streets, EIC 640-643-5400-0000).

4 SC District (South Coast Air Quality Management District, SCAQMD) data, controlled emissions from paved roads at sand 

and gravel processing facilities (Unspecified Paved Roads, EIC 640-636-5400-0000). 

5 Sacramento Area Council of Governments (SACOG) provided Sacramento County 2008 travel fractions.

TABLE 7, continued

2008 Entrained Paved Road Dust Emissions for Total Suspended Particulates (TSP, tons/year)

2008 Paved Road Dust TSP Emissions, Tons/Year (1)

Air

Basin County District Freeway Major Collector

Local, Local 

Urban (2)

Local Rural, (3) 

Sand/Gravel (4) Total

SF Alameda BA 1,305.3 1,121.1 226.5 1,515.2 4,168

Contra Costa BA 835.5 828.1 164.5 1,659.4 3,487

Marin BA 188.4 168.7 84.8 317.3 759

Napa BA 53.4 238.6 92.8 339.7 725

San Francisco BA 282.5 625.4 81.5 515.6 1,505

San Mateo BA 680.8 592.1 116.0 827.1 2,216

Santa Clara BA 1,066.0 1,691.7 201.9 1,946.3 4,906

Solano BA 286.7 175.7 42.5 350.5 856

Sonoma BA 164.0 457.9 180.2 685.6 1,488

SJV (2,3) Fresno SJU 380.3 851.5 250.9 1,122.0 5,962.8 8,567

Kern SJU 300.8 967.2 140.4 310.4 4,015.6 5,734

Kings SJU 60.0 175.4 50.4 73.5 775.7 1,135

Madera SJU 41.6 297.9 45.9 261.5 656.8 1,304

Merced SJU 117.3 388.2 92.0 312.7 1,345.0 2,255

San Joaquin SJU 426.2 502.6 167.6 214.0 2,897.8 4,208

Stanislaus SJU 203.7 390.5 237.7 173.1 2,753.0 3,758

Tulare SJU 86.1 472.9 149.4 503.5 1,792.7 3,005

SCC San Luis Obispo SLO 87.8 391.1 55.3 476.2 1,010

Santa Barbara SB 212.8 551.2 138.3 615.9 1,518

Ventura VEN 428.8 833.3 146.2 1,143.4 2,552

SC (4) Los Angeles SC 5,670.2 3,735.8 456.4 3,737.9 577.9 14,178

Orange SC 2,110.6 1,271.2 80.6 1,520.3 170.7 5,153

Riverside SC 1,023.6 2,516.2 949.1 4,063.7 302.1 8,855

San Bernardino SC 1,152.2 2,638.3 537.5 4,443.8 262.7 9,035

Statewide Totals 23,865 32,922 7,641 44,519 21,513 130,460
Page 19 of 27

1 2008 VMT from EMFAC2011-SG (Sept. 12, 2011). Does not include VMT on roads at sand and gravel processing facilities. 

2 Sacramento Area Council of Governments (SACOG) provided Sacramento County 2008 travel fractions.

TABLE 8

2008 Roadway Travel Fractions and VMT (1) Estimates for California Entrained Paved Road Dust

EMFAC2011

VMT for 2008 (1)

2008 HPMS Travel Fractions

Air

Basin County District

(million VMT 

per year) Freeway Major Collector Local

GB Alpine GBU 15 0.000 0.775 0.118 0.107

Inyo GBU 255 0.002 0.743 0.156 0.099

Mono GBU 144 0.000 0.776 0.085 0.139

LC Lake LAK 622 0.000 0.610 0.278 0.113

LT El Dorado ED 270 0.174 0.572 0.130 0.124

Placer PLA 127 0.408 0.381 0.113 0.097

MD Kern KER 1,448 0.268 0.562 0.082 0.089

Los Angeles AV 4,501 0.453 0.442 0.054 0.051

Riverside MOJ 368 0.478 0.333 0.126 0.063

Riverside SC 422 0.478 0.333 0.126 0.063

San Bernardino MOJ 8,702 0.524 0.340 0.069 0.067

MC Amador AMA 402 0.000 0.763 0.139 0.098

Calaveras CAL 511 0.000 0.688 0.186 0.126

El Dorado ED 1,603 0.174 0.572 0.130 0.124

Mariposa MPA 193 0.000 0.488 0.075 0.437

Nevada NSI 1,023 0.437 0.261 0.167 0.135

Placer PLA 547 0.408 0.381 0.113 0.097

Plumas NSI 213 0.000 0.519 0.273 0.209

Sierra NSI 36 0.140 0.435 0.153 0.272

Tuolumne TUO 561 0.000 0.583 0.246 0.171

NCC Monterey MBU 4,411 0.164 0.572 0.164 0.101

San Benito MBU 734 0.000 0.853 0.082 0.064

Santa Cruz MBU 2,537 0.271 0.476 0.187 0.066

NC Del Norte NCU 221 0.000 0.657 0.227 0.116

Humboldt NCU 1,263 0.222 0.497 0.175 0.106

Mendocino MEN 978 0.062 0.599 0.221 0.118

Sonoma NS 673 0.258 0.470 0.185 0.087

Trinity NCU 159 0.000 0.712 0.082 0.206

NEP Lassen LAS 273 0.000 0.587 0.256 0.157

Modoc MOD 86 0.000 0.453 0.224 0.323

Siskiyou SIS 569 0.453 0.224 0.121 0.201

SV Butte BUT 2,038 0.080 0.557 0.240 0.124

Colusa COL 241 0.609 0.167 0.077 0.147

Glenn GLE 300 0.541 0.209 0.121 0.129

Placer PLA 2,985 0.408 0.381 0.113 0.097

Sacramento (2) SAC 12,914 0.469 0.389 0.075 0.067

Shasta SHA 1,711 0.419 0.401 0.090 0.090

Solano YS 2,066 0.627 0.251 0.061 0.062

Sutter FR 758 0.088 0.628 0.129 0.155

Tehama TEH 733 0.492 0.264 0.148 0.095

Yolo YS 2,063 0.561 0.252 0.086 0.101

Yuba FR 717 0.165 0.503 0.220 0.111

SS Imperial IMP 2,383 0.273 0.453 0.168 0.106

Riverside SC 4,689 0.478 0.333 0.126 0.063

SD San Diego SD 29,665 0.553 0.319 0.080 0.048

TABLE 8 CONTINUES ON NEXT PAGE
Page 20 of 27

1 2008 VMT from EMFAC2011-SG (Sept. 12, 2011). Does not include VMT on roads at sand and gravel processing facilities. 

2 Sacramento Area Council of Governments (SACOG) provided Sacramento County 2008 travel fractions.

TABLE 8, continued

2008 Roadway Travel Fractions and VMT (1) Estimates for California Entrained Paved Road Dust

EMFAC2011

VMT for 2008 (1)

2008 HPMS Travel Fractions

Air

Basin County District

(million VMT 

per year) Freeway Major Collector Local

SF Alameda BA 14,397 0.566 0.317 0.064 0.053

Contra Costa BA 10,082 0.517 0.334 0.066 0.082

Marin BA 2,376 0.497 0.290 0.146 0.067

Napa BA 1,863 0.180 0.524 0.204 0.092

San Francisco BA 4,922 0.360 0.520 0.068 0.053

San Mateo BA 7,543 0.563 0.319 0.063 0.055

Santa Clara BA 15,374 0.434 0.449 0.054 0.064

Solano BA 2,840 0.627 0.251 0.061 0.062

Sonoma BA 3,988 0.258 0.470 0.185 0.087

SJV Fresno SJU 8,024 0.293 0.427 0.126 0.154

Kern SJU 6,890 0.268 0.562 0.082 0.089

Kings SJU 1,398 0.264 0.503 0.144 0.089

Madera SJU 1,844 0.139 0.650 0.100 0.111

Merced SJU 2,949 0.244 0.527 0.125 0.104

San Joaquin SJU 5,808 0.456 0.351 0.117 0.076

Stanislaus SJU 4,208 0.300 0.375 0.229 0.096

Tulare SJU 3,479 0.152 0.545 0.172 0.130

SCC San Luis Obispo SLO 2,569 0.211 0.611 0.086 0.092

Santa Barbara SB 4,398 0.299 0.505 0.127 0.069

Ventura VEN 7,087 0.370 0.469 0.082 0.079

SC Los Angeles SC 76,645 0.453 0.442 0.054 0.051

Orange SC 26,752 0.483 0.431 0.027 0.059

Riverside SC 13,114 0.478 0.333 0.126 0.063

San Bernardino SC 13,544 0.524 0.340 0.069 0.067

Statewide Total VMT (millions) 339,224

Statewide Average Travel Fractions 0.291 0.468 0.131 0.110
Page 21 of 27

1 For Major, Collector and Local roads, the portion of Los Angeles County in the SC District (South Coast Air Quality Management District, SCAQMD) 

and all portions of Orange, Riverside and San Bernardino counties use silt loading values derived by the SCAQMD from a subset of measurements 

collected in the SCAQMD and Riverside County. Silt loading measurements used for this update are presented in Appendix A, Table 1. See Table 3

for more information on how silt loading values were derived. 

2 The SJU District (San Joaquin Valley Air Pollution Control District) splits local roads into urban and rural classes and uses separate silt loading 

values. A higher silt loading value derived from AP-42 data is used to compute emissions for rural local roads due to anticipated higher loading levels.

3 SC District (SCAQMD) uses a composite emission factor for paved roads at sand and gravel processing facilities.

TABLE 9

2008 Silt Loadings and PM10 Emission Factors for California Entrained Paved Road Dust Estimates

Silt Loadings (g/m2) and PM10 Emission Factors (EF; lbs PM10/106VMT)

Freeway Major (1) Collector (1)

Local, Local 

Urban (1,2)

Local Rural (2) 

Sand/Gravel Proc. (3)

Average 

Vehicle

Air

Basin County District

Silt 

Load EF

Silt 

Load EF

Silt 

Load EF

Silt 

Load EF

Silt 

Load EF

Weight

(tons)

GB Alpine GBU 0.02 145.3 0.032 222.8 0.032 222.8 0.32 1,811.2 2.4

Inyo GBU 0.02 149.9 0.032 229.9 0.032 229.9 0.32 1,868.6 2.4

Mono GBU 0.02 148.7 0.032 228.1 0.032 228.1 0.32 1,854.2 2.4

LC Lake LAK 0.02 145.7 0.032 223.5 0.032 223.5 0.32 1,816.4 2.4

LT El Dorado ED 0.02 145.7 0.032 223.5 0.032 223.5 0.32 1,816.4 2.4

Placer PLA 0.02 144.8 0.032 222.0 0.032 222.0 0.32 1,804.7 2.4

MD Kern KER 0.02 150.3 0.032 230.5 0.032 230.5 0.32 1,873.8 2.4

Los Angeles AV 0.02 150.3 0.032 230.5 0.032 230.5 0.32 1,873.8 2.4

Riverside (1) MOJ 0.02 151.0 0.080 533.3 0.080 533.3 0.84 4,531.5 2.4

Riverside (1) SC 0.02 151.0 0.080 533.3 0.080 533.3 0.84 4,531.5 2.4

San Bernardino (1) MOJ 0.02 150.4 0.080 531.1 0.080 531.1 0.84 4,512.7 2.4

MC Amador AMA 0.02 146.1 0.032 224.1 0.032 224.1 0.32 1,821.6 2.4

Calaveras CAL 0.02 145.3 0.032 222.8 0.032 222.8 0.32 1,811.2 2.4

El Dorado ED 0.02 145.9 0.032 223.8 0.032 223.8 0.32 1,819.0 2.4

Mariposa MPA 0.02 145.6 0.032 223.3 0.032 223.3 0.32 1,815.1 2.4

Nevada NSI 0.02 144.1 0.032 221.1 0.032 221.1 0.32 1,796.8 2.4

Placer PLA 0.02 145.2 0.032 222.7 0.032 222.7 0.32 1,809.9 2.4

Plumas NSI 0.02 145.0 0.032 222.3 0.032 222.3 0.32 1,807.3 2.4

Sierra NSI 0.02 144.5 0.032 221.7 0.032 221.7 0.32 1,802.0 2.4

Tuolumne TUO 0.02 146.0 0.032 223.2 0.032 223.9 0.32 1,820.3 2.4

NCC Monterey MBU 0.02 147.1 0.032 225.6 0.032 225.6 0.32 1,833.4 2.4

San Benito MBU 0.02 147.5 0.032 226.2 0.032 226.2 0.32 1,838.6 2.4

Santa Cruz MBU 0.02 146.0 0.032 223.9 0.032 223.9 0.32 1,820.3 2.4

NC Del Norte NCU 0.02 141.2 0.032 216.6 0.032 216.6 0.32 1,760.3 2.4

Humboldt NCU 0.02 140.2 0.032 215.0 0.032 215.0 0.32 1,747.2 2.4

Mendocino MEN 0.02 140.8 0.032 215.9 0.032 215.9 0.32 1,755.1 2.4

Sonoma NS 0.02 145.0 0.032 222.3 0.032 222.3 0.32 1,807.3 2.4

Trinity NCU 0.02 144.0 0.032 220.9 0.032 220.9 0.32 1,795.5 2.4

NEP Lassen LAS 0.02 146.6 0.032 224.9 0.032 224.9 0.32 1,828.1 2.4

Modoc MOD 0.02 144.9 0.032 222.2 0.032 222.2 0.32 1,806.0 2.4

Siskiyou SIS 0.02 142.8 0.032 219.0 0.032 219.0 0.32 1,779.9 2.4

SV Butte BUT 0.02 146.2 0.032 224.3 0.032 224.3 0.32 1,822.9 2.4

Colusa COL 0.02 147.0 0.032 225.4 0.032 225.4 0.32 1,832.1 2.4

Glenn GLE 0.02 146.2 0.032 224.3 0.032 224.3 0.32 1,822.9 2.4

Placer PLA 0.02 145.9 0.032 223.8 0.032 223.8 0.32 1,819.0 2.4

Sacramento SAC 0.02 146.9 0.032 225.2 0.032 225.2 0.32 1,830.8 2.4

Shasta SHA 0.02 144.2 0.032 221.2 0.032 221.2 0.32 1,798.1 2.4

Solano YS 0.02 146.7 0.032 225.1 0.032 225.1 0.32 1,829.4 2.4

Sutter FR 0.02 145.0 0.032 222.3 0.032 222.3 0.32 1,807.3 2.4

Tehama TEH 0.02 145.4 0.032 223.0 0.032 223.0 0.32 1,812.5 2.4

Yolo YS 0.02 146.7 0.032 225.1 0.032 225.1 0.32 1,829.4 2.4

Yuba FR 0.02 146.2 0.032 224.3 0.032 224.3 0.32 1,822.9 2.4

TABLE 9 CONTINUES ON NEXT PAGE
Page 22 of 27

1 For Major, Collector and Local roads, the portion of Los Angeles County in the SC District (South Coast Air Quality Management District, SCAQMD) 

and all portions of Orange, Riverside and San Bernardino counties use silt loading values derived by the SCAQMD from a subset of measurements 

collected in the SCAQMD and Riverside County. Silt loading measurements used for this update are presented in Appendix A, Table 1. See Table 3

for more information on how silt loading values were derived. 

2 The SJU District (San Joaquin Valley Air Pollution Control District) splits local roads into urban and rural classes and uses separate silt loading 

values. A higher silt loading value derived from AP-42 data is used to compute emissions for rural local roads due to anticipated higher loading levels.

3 SC District (SCAQMD) uses a composite emission factor for paved roads at sand and gravel processing facilities.

TABLE 9, continued

2008 Silt Loadings and PM10 Emission Factors for California Entrained Paved Road Dust Estimates

Silt Loadings (g/m2) and PM10 Emission Factors (EF; lbs PM10/106VMT)

Freeway Major (1) Collector (1) Local, Local 

Urban (1,2)

Local Rural (2) 

Sand/Gravel Proc. (3)

Average 

Vehicle

Air

Basin County District

Silt 

Load EF

Silt 

Load EF

Silt 

Load EF

Silt 

Load EF

Silt 

Load EF

Weight

(tons)

SS Imperial IMP 0.02 151.7 0.032 232.6 0.032 232.6 0.32 1,890.8 2.4

Riverside (1) SC 0.02 151.0 0.080 533.3 0.080 533.3 0.84 4,531.5 2.4

SD San Diego SD 0.02 148.4 0.032 227.6 0.032 227.6 0.32 1,850.3 2.4

SF Alameda BA 0.02 146.4 0.032 224.6 0.032 224.6 0.32 1,825.5 2.4

Contra Costa BA 0.02 146.5 0.032 224.8 0.032 224.8 0.32 1,826.8 2.4

Marin BA 0.02 145.9 0.032 223.8 0.032 223.8 0.32 1,819.0 2.4

Napa BA 0.02 145.7 0.032 223.5 0.032 223.5 0.32 1,816.4 2.4

San Francisco BA 0.02 145.8 0.032 223.6 0.032 223.6 0.32 1,817.7 2.4

San Mateo BA 0.02 146.5 0.032 224.8 0.032 224.8 0.32 1,826.8 2.4

Santa Clara BA 0.02 146.1 0.032 224.1 0.032 224.1 0.32 1,821.6 2.4

Solano BA 0.02 147.2 0.032 225.7 0.032 225.7 0.32 1,834.7 2.4

Sonoma BA 0.02 145.6 0.032 223.3 0.032 223.3 0.32 1,815.1 2.4

SJV (2) Fresno SJU 0.02 148.1 0.032 227.2 0.032 227.2 0.32 1,846.4 1.6 7,987.1 2.4

Kern SJU 0.02 148.9 0.032 228.4 0.032 228.4 0.32 1,856.8 1.6 8,032.3 2.4

Kings SJU 0.02 148.8 0.032 228.3 0.032 228.3 0.32 1,855.5 1.6 8,026.6 2.4

Madera SJU 0.02 148.2 0.032 227.3 0.032 227.3 0.32 1,847.7 1.6 7,992.8 2.4

Merced SJU 0.02 148.9 0.032 228.4 0.032 228.4 0.32 1,856.8 1.6 8,032.3 2.4

San Joaquin SJU 0.02 147.1 0.032 225.6 0.032 225.6 0.32 1,833.4 1.6 7,930.7 2.4

Stanislaus SJU 0.02 147.4 0.032 226.0 0.032 226.0 0.32 1,837.3 1.6 7,947.6 2.4

Tulare SJU 0.02 148.6 0.032 228.0 0.032 228.0 0.32 1,852.9 1.6 8,015.4 2.4

SCC San Luis Obispo SLO 0.02 148.4 0.032 227.6 0.032 227.6 0.32 1,850.3 2.4

Santa Barbara SB 0.02 148.0 0.032 227.0 0.032 227.0 0.32 1,845.1 2.4

Ventura VEN 0.02 149.6 0.032 229.4 0.032 229.4 0.32 1,864.7 2.4

SC Los Angeles SC 0.02 149.3 0.013 100.9 0.013 100.9 0.14 877.0 --- --- 2.4

(1,3) Orange SC 0.02 149.4 0.013 100.9 0.013 100.9 0.14 877.6 --- --- 2.4

Riverside SC 0.02 149.3 0.080 527.0 0.080 527.0 0.84 4,478.2 --- --- 2.4

San Bernardino SC 0.02 148.5 0.080 524.0 0.080 524.0 0.84 4,456.2 --- --- 2.4
Page 23 of 27

1 Average days per year with > 0.01 inch precipitation over years of record, Western Regional Climate Center data, 

 http://www.wrcc.dri.edu/ 

TABLE 10

Average Days per Year that California Counties Receive 0.01 Inch

or Greater Precipitation Over Years of Record (1)

Average days 

per year with 

Average days 

per year with 

Air Basin District County

>0.01 inch 

precipitation Air Basin District County

>0.01 inch 

precipitation

GB GBU Alpine 72 SF BA Alameda 61

GBU Inyo 28 BA Contra Costa 60

GBU Mono 39 BA Marin 66

LC LAK Lake 68 BA Napa 68

LT ED El Dorado 68 BA San Francisco 67

PLA Placer 77 BA San Mateo 60

MD KER Kern 24 BA Santa Clara 64

AV Los Angeles 24 BA Solano 54

MOJ Riverside 17 BA Sonoma 69

SC Riverside 17 SJV SJU Fresno 45

MOJ San Bernardino 23 SJU Kern 37

MC AMA Amador 64 SJU Kings 38

CAL Calaveras 72 SJU Madera 44

ED El Dorado 66 SJU Merced 51

MPA Mariposa 69 SJU San Joaquin 55

NSI Nevada 83 SJU Stanislaus 52

PLA Placer 73 SJU Tulare 40

NSI Plumas 75 SCC SLO San Luis Obispo 42

NSI Sierra 79 SB Santa Barbara 46

TUO Tuolumne 65 VEN Ventura 31

NCC MBU Monterey 55 SC SC Los Angeles 34

MBU San Benito 51 SC Orange 33

MBU Santa Cruz 65 SC Riverside 34

NC NCU Del Norte 111 SC San Bernardino 41

NCU Humboldt 121

MEN Mendocino 115

NS Sonoma 75

NCU Trinity 84

NEP LAS Lassen 59

MOD Modoc 76

SIS Siskiyou 96

SV BUT Butte 63

COL Colusa 56

GLE Glenn 63

PLA Placer 66

SAC Sacramento 57

SHA Shasta 82

YS Solano 58

FR Sutter 75

TEH Tehama 71

YS Yolo 58

FR Yuba 63

SS IMP Imperial 11

SC Riverside 17

SD SD San Diego 42
Page 24 of 27

1 Western Regional Climate Center data (http://www.wrcc.dri.edu/), average days per month with rainfall of 0.01 inch or 

greater, based on California meteorological station level rainfall data for years of record.

2 Normalized Rainfall per Month = 1- [Rain days per month/annual rain days]

Monthly Rainfall Fraction = [Normalized Rainfall per Month]/[Total Normalized Rainfall] 

Table 11. Table 11. Temporal Profile for Paved Road Dust Emissions, 

Based on Monthly Days of Rain (1,2)

Air Monthly Rainfall Fraction (1,2)

Basin County District Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

GB Alpine GBU 0.078 0.079 0.081 0.083 0.083 0.086 0.087 0.087 0.086 0.086 0.083 0.081

Inyo GBU 0.078 0.078 0.081 0.085 0.085 0.088 0.085 0.085 0.085 0.085 0.085 0.081

Mono GBU 0.079 0.079 0.082 0.084 0.084 0.084 0.084 0.084 0.086 0.086 0.084 0.082

LC Lake LAK 0.074 0.080 0.078 0.082 0.086 0.088 0.091 0.091 0.090 0.086 0.080 0.076

LT El Dorado ED 0.080 0.082 0.080 0.078 0.083 0.088 0.088 0.090 0.090 0.086 0.080 0.075

Placer PLA 0.078 0.079 0.079 0.082 0.084 0.086 0.090 0.089 0.087 0.085 0.082 0.079

MD Kern KER 0.075 0.075 0.075 0.083 0.087 0.091 0.091 0.087 0.087 0.087 0.083 0.079

Los Angeles AV 0.076 0.080 0.076 0.080 0.087 0.091 0.087 0.087 0.087 0.087 0.080 0.080

Riverside MOJ 0.074 0.080 0.080 0.085 0.090 0.090 0.085 0.080 0.085 0.085 0.085 0.080

Riverside SC 0.074 0.080 0.080 0.085 0.090 0.090 0.085 0.080 0.085 0.085 0.085 0.080

San Bernardino MOJ 0.075 0.079 0.079 0.083 0.087 0.091 0.083 0.083 0.087 0.087 0.083 0.083

MC Amador AMA 0.075 0.077 0.078 0.081 0.085 0.089 0.091 0.089 0.089 0.087 0.081 0.077

Calaveras CAL 0.078 0.078 0.077 0.081 0.084 0.088 0.091 0.090 0.088 0.086 0.081 0.078

El Dorado ED 0.077 0.077 0.077 0.081 0.085 0.088 0.091 0.091 0.089 0.085 0.081 0.077

Mariposa MPA 0.079 0.079 0.078 0.080 0.084 0.088 0.088 0.089 0.087 0.086 0.082 0.080

Nevada NSI 0.077 0.078 0.078 0.081 0.086 0.088 0.091 0.090 0.089 0.086 0.080 0.078

Placer PLA 0.077 0.078 0.077 0.081 0.085 0.088 0.091 0.090 0.088 0.086 0.080 0.078

Plumas NSI 0.079 0.079 0.079 0.081 0.084 0.087 0.090 0.090 0.088 0.085 0.081 0.078

Sierra NSI 0.078 0.079 0.079 0.082 0.083 0.087 0.090 0.090 0.087 0.085 0.081 0.078

Tuolumne TUO 0.075 0.077 0.077 0.082 0.086 0.089 0.091 0.091 0.089 0.086 0.079 0.077

NCC Monterey MBU 0.076 0.076 0.076 0.081 0.086 0.089 0.091 0.091 0.089 0.086 0.081 0.078

San Benito MBU 0.077 0.075 0.077 0.082 0.087 0.089 0.091 0.091 0.089 0.086 0.080 0.077

Santa Cruz MBU 0.076 0.077 0.077 0.083 0.087 0.088 0.091 0.090 0.088 0.087 0.081 0.077

NC Del Norte NCU 0.079 0.080 0.079 0.083 0.084 0.087 0.089 0.088 0.088 0.084 0.080 0.079

Humboldt NCU 0.079 0.080 0.079 0.082 0.085 0.086 0.089 0.089 0.088 0.085 0.080 0.079

Mendocino MEN 0.078 0.080 0.080 0.083 0.085 0.088 0.089 0.088 0.087 0.085 0.080 0.078

Sonoma NS 0.076 0.078 0.078 0.081 0.086 0.090 0.091 0.090 0.088 0.086 0.079 0.078

Trinity NCU 0.078 0.079 0.079 0.082 0.085 0.088 0.090 0.089 0.088 0.084 0.080 0.078

NEP Lassen LAS 0.079 0.079 0.080 0.083 0.083 0.085 0.089 0.089 0.088 0.085 0.082 0.079

Modoc MOD 0.080 0.080 0.080 0.081 0.083 0.085 0.089 0.089 0.087 0.085 0.081 0.080

Siskiyou SIS 0.078 0.080 0.080 0.082 0.084 0.087 0.090 0.089 0.088 0.084 0.080 0.078

SV Butte BUT 0.075 0.076 0.078 0.082 0.085 0.088 0.091 0.091 0.089 0.085 0.081 0.078

Colusa COL 0.075 0.076 0.078 0.083 0.086 0.089 0.091 0.091 0.089 0.086 0.080 0.076

Glenn GLE 0.075 0.078 0.079 0.082 0.085 0.088 0.091 0.090 0.090 0.085 0.079 0.077

Placer PLA 0.076 0.077 0.077 0.081 0.086 0.088 0.091 0.091 0.088 0.086 0.080 0.077

Sacramento SAC 0.075 0.077 0.077 0.083 0.086 0.089 0.091 0.091 0.089 0.086 0.080 0.077

Shasta SHA 0.076 0.079 0.078 0.081 0.083 0.088 0.091 0.090 0.090 0.086 0.081 0.078

Solano YS 0.074 0.077 0.077 0.083 0.086 0.089 0.091 0.091 0.089 0.086 0.080 0.075

Sutter FR 0.076 0.079 0.077 0.081 0.085 0.088 0.091 0.090 0.088 0.086 0.080 0.079

Tehama TEH 0.077 0.078 0.078 0.082 0.086 0.088 0.091 0.090 0.088 0.086 0.079 0.077

Yolo YS 0.075 0.077 0.078 0.083 0.086 0.089 0.091 0.091 0.089 0.086 0.080 0.075

Yuba FR 0.075 0.078 0.078 0.082 0.087 0.089 0.091 0.089 0.089 0.085 0.079 0.076

SS Imperial IMP 0.075 0.075 0.075 0.092 0.092 0.092 0.083 0.083 0.083 0.083 0.083 0.083

Riverside SC 0.074 0.074 0.079 0.085 0.090 0.090 0.090 0.085 0.085 0.085 0.085 0.079

SD San Diego SD 0.076 0.076 0.076 0.080 0.087 0.089 0.091 0.091 0.089 0.087 0.082 0.078

TABLE 11 CONTINUES ON NEXT PAGE
Page 25 of 27

1 Western Regional Climate Center data (http://www.wrcc.dri.edu/), average days per month with rainfall of 0.01 inch or 

greater, based on California meteorological station level rainfall data for years of record.

2 Normalized Rainfall per Month = 1- [Rain days per month/annual rain days]

Monthly Rainfall Fraction = [Normalized Rainfall per Month]/[Total Normalized Rainfall] 

Table 11. Temporal Profile for Paved Road Dust Emissions, 

Based on Monthly Days of Rain (1,2), continued

Air Monthly Rainfall Fraction (1,2)

Basin County District Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

SF Alameda BA 0.076 0.077 0.077 0.082 0.088 0.089 0.091 0.089 0.089 0.085 0.079 0.077

Contra Costa BA 0.076 0.077 0.077 0.082 0.086 0.089 0.091 0.091 0.089 0.086 0.080 0.076

Marin BA 0.074 0.077 0.077 0.083 0.087 0.090 0.091 0.091 0.090 0.085 0.080 0.076

Napa BA 0.077 0.075 0.077 0.081 0.087 0.089 0.091 0.091 0.089 0.087 0.079 0.076

San Francisco BA 0.076 0.076 0.077 0.083 0.087 0.090 0.091 0.090 0.088 0.085 0.080 0.077

San Mateo BA 0.076 0.077 0.077 0.082 0.086 0.089 0.091 0.091 0.089 0.086 0.080 0.076

Santa Clara BA 0.078 0.074 0.077 0.080 0.087 0.090 0.091 0.091 0.090 0.087 0.080 0.077

Solano BA 0.072 0.077 0.077 0.082 0.088 0.089 0.091 0.091 0.089 0.088 0.079 0.076

Sonoma BA 0.075 0.078 0.078 0.083 0.087 0.089 0.091 0.091 0.089 0.085 0.079 0.076

SJV Fresno SJU 0.075 0.075 0.077 0.083 0.087 0.089 0.091 0.091 0.089 0.087 0.081 0.077

Kern SJU 0.076 0.076 0.076 0.081 0.086 0.090 0.090 0.090 0.088 0.086 0.083 0.078

Kings SJU 0.076 0.076 0.076 0.081 0.086 0.090 0.090 0.090 0.090 0.086 0.081 0.076

Madera SJU 0.074 0.076 0.076 0.083 0.087 0.089 0.091 0.091 0.089 0.087 0.081 0.076

Merced SJU 0.073 0.077 0.077 0.082 0.087 0.091 0.091 0.091 0.089 0.087 0.080 0.077

San Joaquin SJU 0.076 0.076 0.077 0.082 0.087 0.089 0.091 0.091 0.089 0.086 0.079 0.077

Stanislaus SJU 0.074 0.075 0.077 0.082 0.088 0.089 0.091 0.091 0.089 0.086 0.081 0.077

Tulare SJU 0.075 0.075 0.077 0.082 0.086 0.091 0.091 0.091 0.088 0.086 0.082 0.077

SCC San Luis Obispo SLO 0.074 0.074 0.076 0.082 0.087 0.091 0.091 0.091 0.089 0.087 0.080 0.078

Santa Barbara SB 0.075 0.075 0.075 0.081 0.087 0.089 0.091 0.091 0.089 0.087 0.081 0.079

Ventura VEN 0.073 0.073 0.076 0.082 0.088 0.091 0.091 0.091 0.088 0.088 0.082 0.079

SC Los Angeles SC 0.075 0.075 0.075 0.083 0.088 0.091 0.091 0.091 0.088 0.086 0.080 0.078

Orange SC 0.071 0.074 0.077 0.082 0.088 0.088 0.091 0.091 0.091 0.085 0.085 0.077

Riverside SC 0.075 0.075 0.077 0.083 0.085 0.091 0.091 0.091 0.088 0.085 0.083 0.077

San Bernardino SC 0.077 0.075 0.075 0.082 0.086 0.088 0.091 0.088 0.088 0.084 0.084 0.080
Page 26 of 27

1 Researcher: 

MRI = Midwest Research Institute 

(http://www.arb.ca.gov/ei/areasrc/arbmiscprocpaverddstbkgrnd.pdf)

UCR = Univ. of California, Riverside 

(http://aqp.engr.ucdavis.edu/Documents/DraftRoadDustreport.pdf)

UCD = Univ. of California, Davis 

(http://aqp.engr.ucdavis.edu/Documents/pm10_hotspot_Sunrise.pdf)

Appendix A. ARB’s Emissions Estimation Methodology, Section 7.9, Paved Road Dust

Table 1. 1995-1997 Silt Loading Values 

Silt Loading

Location Date (g/m2) Sampling Location Researcher(1)

HIGH Average Daily Traffic (ADT) Roads (> 5,000 vehicle passes/day)

South Coast Apr-95 0.012 Composite of 4 roads of same class MRI

South Coast Jun-95 0.015 Repeat sample of above roads MRI

South Coast Jun-95 0.011 Composite of 4 roads of same class MRI

South Coast Jun-95 0.046 Composite of 4 roads of same class MRI

Bakersfield Apr-95 0.054 Composite of 4 roads of same class MRI

Bakersfield Jul-95 0.015 Repeat sample of above roads MRI

Bakersfield Jul-95 0.051 Composite of 4 roads of same class MRI

Bakersfield Jul-95 0.039 Composite of 4 roads of same class MRI

Coachella Valley Apr-95 0.027 Composite of 4 roads of same class MRI

Coachella Valley Jul-95 0.037 Repeat sample of above roads MRI

Coachella Valley Jul-95 0.082 Composite of 4 roads of same class MRI

Coachella Valley Jul-95 0.03 Composite of 4 roads of same class MRI

Sacramento 1997 0.0332 Sunrise Crosswalk North UCD

Sacramento 1997 0.0261 Sunrise Crosswalk south UCD

Sacramento 1997 0.0184 Greenback Crosswalk West UCD

Sacramento 1997 0.0136 Greenback Crosswalk East UCD

Sacramento 8/23/1995 0.0543 Florin Rd East UCD

Sacramento 8/23/1995 0.0034 Florin Road West UCD

Sacramento 8/23/1995 0.0016 Stockton Blvd South UCD

Sacramento 8/23/1995 0.002 Stockton Blvd North UCD

Riverside 3/18/1997 0.065 Canyon Crest Drive UCR

Riverside 6/5/1997 0.085 Canyon Crest Drive UCR

Riverside 6/19/1996 0.00593 Main Street UCR

Riverside 9/3/1996 0.00593 Main Street UCR

Riverside 3/17/1997 0.2 Riverside Street UCR

Riverside 5/29/1997 0.17 Riverside Street UCR

Riverside 3/19/1997 0.19 Riverside Street UCR

Riverside 6/4/1997 0.085 Riverside Street UCR

Riverside 5/27/1997 0.38 Fogg Street UCR

Riverside 3/26/1997 0.13 Fogg Street UCR

Riverside 6/3/1997 0.14 Fogg Street UCR

Geometric mean of high ADT roads = 0.032 g/m2, used as California statewide default silt loading for 

Major and Collector roads. See Table 3 for information on deriving statewide, district and county 

specific silt loading values.

APPENDIX A, TABLE 1 CONTINUES ON NEXT PAGE
Page 27 of 27

1 Researcher: 

MRI = Midwest Research Institute 

(http://www.arb.ca.gov/ei/areasrc/arbmiscprocpaverddstbkgrnd.pdf)

UCR = Univ. of California, Riverside 

(http://aqp.engr.ucdavis.edu/Documents/DraftRoadDustreport.pdf)

UCD = Univ. of California, Davis 

(http://aqp.engr.ucdavis.edu/Documents/pm10_hotspot_Sunrise.pdf)

Appendix A. ARB’s Emissions Estimation Methodology, Section 7.9, Paved Road Dust

Table 1. 1995-1997 Silt Loading Values, continued

Silt Loading

Location Date (g/m2) Sampling Location Researcher(1)

LOW ADT Roads (< 5,000 vehicle passes/day)

South Coast Apr-95 0.18 Composite of 4 roads of same class MRI

South Coast Jun-95 0.05 Repeat sample of above roads MRI

South Coast Jun-95 0.17 Composite of 4 roads of same class MRI

South Coast Jun-95 0.14 Composite of 4 roads of same class MRI

Bakersfield Apr-95 0.52 Composite of 4 roads of same class MRI

Bakersfield Jul-95 0.19 Repeat sample of above roads MRI

Bakersfield Jul-95 0.94 Composite of 4 roads of same class MRI

Bakersfield Jul-95 0.41 Composite of 4 roads of same class MRI

Coachella Valley Jul-95 0.42 Repeat sample of above roads MRI

Coachella Valley Jul-95 0.35 Composite of 4 roads of same class MRI

Coachella Valley Jul-95 0.2 Composite of 4 roads of same class MRI

Mean of low ADT roads = 0.32 g/m2, used as California statewide default slit loading for Local roads.

See Table 3 for information on deriving statewide, district and county specific silt loading values