Appendix 9-1 of Delaware 8-Hour Ozone SIP revision 

Delaware State Implementation Plan for Attainment of the 8-Hour Ozone National 

Ambient Air Quality Standard, Revision for Establishment of 2008 and 2009 Mobile 

Source Emission Budgets 

May 2007 

This document assigns the on-road mobile source emissions budgets for each county in 

Delaware as part of the Philadelphia-Wilmington-Atlantic City, PA-NJ-MD-DE 

moderate non-attainment area for the 8 hour ozone National Ambient Air Quality 

Standard (NAAQ).S Section 176 of the Clean Air Act (42 USC 7506) and Title 40 Parts 

51 and 93 of the Code of Federal Regulations are the basis for the authority to establish

mobile emission budgets in the Delaware State Implementation Plan (SIP) to attain the 

ozone standard. The on-road mobile source emissions budgets will be made a part of the 

State Implementation Plan to attain the 8 hour ozone standard by the year 2009 and to 

reach further reasonable progress towards attaining the standard by 2008. Therefore, the 

tables below will assign budgets for each year and for each county. The mobile source 

emissions are projected for these years using the USEPA mobile emission model, 

“Mobile 6.2” for calculating emission factors and the “Peninsula Travel Demand Model” 

for calculating future vehicle miles traveled (VMT). 

Mobile 6.2 calculates emission factors for each USEPA vehicle type traveling on 

designated federal highway classifications road types in Delaware. Depending on the 

county, Delaware has up to 11 different federal highway classifications for its roads. 

There are two pollutants that are calculated using the mobile computer model. Volatile 

organic compounds (VOC) and nitrogen oxide (NOx) emission factors are generated 

from the Mobile 6.2 computer model. These pollutants are modeled because they are the 

precursors to form ground level ozone. A sample emission factor output for New Castle 

County for nitrogen oxides is listed below, for the projection year of 2009. 

New Castle County 

Projected 2009 Mobile Emission Factors 

Nitrogen Oxides (NOx) Grams/Mile 

USEPA Vehicle Type*

Federal Highway Class. LDGV LDGT

1-2 

LDGT 

3-4 

HDGV LDDV LDDT HDDV MC

Other Principal ArterialRural 0.51 0.37 0.42 0.38 0.19 0.23 0.22 3.35

Minor Arterial-Rural 0.54 0.39 0.44 0.42 0.20 0.25 0.25 2.75

Major Collector-Rural 0.55 0.39 0.45 0.44 0.21 0.26 0.27 2.79

Minor Collector-Rural 0.57 0.41 0.47 0.48 0.22 0.28 0.30 2.90

Local-Rural 0.83 0.60 0.70 1.08 0.37 0.51 0.66 4.21

Interstate-Urban 0.52 0.38 0.43 0.39 0.19 0.23 0.23 3.19

Other Freeway &

Expressways-Urban 

0.51 0.38 0.42 0.39 0.19 0.23 0.23 3.41

Other Principal Arterial- 0.55 0.39 0.45 0.44 0.21 0.26 0.27 2.79

1
Urban 

Minor 0.57 0.41 0.47 0.48 0.22 0.28 0.31 2.90

Collector-Urban 0.57 0.41 0.47 0.49 0.22 0.28 0.31 2.91

Local 0.82 0.59 0.69 1.08 0.37 0.51 0.66 4.21

*Description of vehicle types is at the end of this document 

A travel demand model for the State is maintained by the Delaware Department of

Transportation. The model applies a variety of data regarding roadway network 

conditions, vehicular travel patterns, automobile ownership, and the location of 

population and employment sites. The model follows the “traditional four-step process” 

of trip generation, distribution, mode split, and assignment that is commonly used 

throughout the transportation planning industry. A similar table as above is generated for

VMT according to USEPA vehicle type and federal highway classifications. The two 

matrices are incorporated to calculate tons per-day emissions for each pollutant. 

There are numerous input criteria that go into the mobile model that affect the 

calculations. The major inputs are the vehicle emission control programs and clean fuel

standards that are currently used or will be used for controlling and reducing vehicle

emissions. They include: National Low Emission Vehicle Program and Tier 2 Motor 

Vehicle Controls (light duty vehicles), reformulated gas program, low sulfur gasoline

program, ultra-low sulfur diesel fuel program, heavy duty engine control program 

beginning in 2007 reducing particulate matter and in 2010 reducing nitrogen oxides to 

their lowest levels. The State also has since 1983 inspected vehicles for tailpipe 

emissions. Currently as part of the vehicle emission inspection a vehicle on-board 

diagnostic system is checked for any diagnostic trouble codes which if present requires 

the vehicle to be repaired. 

The following tables assign the on-road mobile emission budgets for milestone years of 

2008 and 2009 for each county in Delaware. 

2008 On-road Vehicle Mobile Emission Budgets for Delaware 

(Emission in tons per day, VMT in miles per day) 

Pollutant Kent New Castle Sussex DE Total 

VOC 4.14 10.61 7.09 21.84

NOX 9.68 21.35 12.86 43.89

VMT 5,520,573 16,917,040 8,450,950 30,888,563

2009 On-road Vehicle Mobile Emission Budgets for Delaware 

(Emission in tons per day, VMT in miles per day) 

Pollutant Kent New Castle Sussex DE Total 

2
VOC 3.95 9.89 7.05 20.89

NOX 9.04 19.23 11.93 40.2

VMT 5,703,033 17,122,179 8,541,828 31,367,040

Supporting documents, including Mobile 6.2 input, output and data files as well as 

spreadsheet calculation files, can be obtained by request in writing to Philip Wheeler, Air 

Quality Management Section, 156 South State Street, Dover, Delaware 19904 or e-mail

Philip.Wheeler@state.de.us. 

Description of Vehicle Types

LDGV Light-Duty Gasoline Vehicles (Passenger Cars) 

LDGT 1-2 Light-Duty Gasoline Trucks 1 (0-6,000 lbs. GVWR, 0-3,750 lbs. LVW)

Light-Duty Gasoline Trucks 2 (0-6,000 lbs. GVWR, 3,751-5,750 lbs. LVW)

LDGT 3-4 Light-Duty Gasoline Trucks 3 (6,001-8,500 lbs. GVWR, 0-5,750 lbs. 

ALVW) Light-Duty Gasoline Trucks 4 (6,001-8,500 lbs. GVWR, 5,751 lbs. 

and greater ALVW) 

HDGV Heavy-Duty Gasoline Vehicles (8,501-80,000 lbs. GVWR) 

LDDV Light-Duty Diesel Vehicles (Passenger Cars) Light-Duty Diesel Vehicles (Passenger Cars) 

LDDT Light-Duty Diesel Trucks (0-8,500 lbs. GVWR)

HDDV Heavy-Duty Diesel Vehicles (8,501-80,000 lbs. GVWR) 

MC Motorcycles

GWWR- Gross Vehicle Weight Rating 

LVW – Loaded Vehicle Weight 

ALVW - Adjusted Loaded Vehicle Weight 

3