Updates to the Off-Road Emissions Model

This page last reviewed April 14, 2010

This page summarizes the major revisions associated with the development of OFFROAD. Each major revision has a brief description, background information, resulting inventory effects, detailed technical documentation, and a staff contact.



Addition of Evaporative Emissions for Small Off-Road Engines

DESCRIPTION:

The OFFROAD Model is used to estimate the contributions of emissions of various equipment types to the overall off-road emissions inventory. With the exception of gas cans, the OFFROAD Model does not currently account for evaporative hydrocarbons. This is primarily due to the lack of test data.

In support of pending regulation, however, Air Resources Board (ARB or Board) staff has performed a number of evaporative tests of small off-road equipment. In addition, a research project performed by the Automotive Testing Laboratories (ATL) for the ARB entitled "Collection of Evaporative Emissions Data from Off-Road Equipment," has recently been completed. It is the information from these projects that serve as the basis for the proposed modification to the off-road emissions inventory. These changes result in an increase in emissions.

INVENTORY EFFECTS:

Addition of Evaporative Emissons for Small Off-Road Engines
Statewide Annual Average (tons per day)

Emission Process 1999 2010 2020
Hot Soak 5.26 6.02 6.51
Diurnal 8.83 10.72 11.71
Resting 5.50 7.18 7.98
Running 7.52 8.66 9.51
Total 27.11 32.58 35.71


Technical Documentation:  Addition of Evaporative Emissions for Small Off-Road Engines

Staff Contact:  Walter Wong



Proposed Update:
Change in Populaton and Activity Factors for Lawn and Garden Equipment

DESCRIPTION:

Under a grant from the United States Environmental Protection Agency (U.S. EPA), staff of the Air Resources Board (ARB or Board) conducted a survey of California households to determine the population and usage of lawn and garden equipment. Over 15,000 surveys were sent to randomly selected households. A subset of survey respondents also agreed to install instrumentation capable of electronically recording the date, time, and duration of usage on their lawn and garden equipment.

An analysis of the survey responses were compared to the current estimates used in the OFFROAD Model for lawn and garden equipment. The results suggest that the OFFROAD Model may understate both the current population and usage of several equipment types within the lawn and garden category. The current estimates are based on information provided by Booz-Allen Hamilton (BAH) as outlined in their report entitled "Off-Road Mobile Equipment Emission Inventory Estimate". Staff is proposing to use the survey results to update the population and activity estimates within the OFFROAD Model. These changes result in an increase in emissions.

INVENTORY EFFECTS:

Change in Population and Activity Factors for Lawn and Garden
Statewide Annual Average (tons per day)

  Exhaust Emissons Evaporative Emissions
  HC CO NOx PM Diurnal Rest Loss Hot Soak Run Loss
Year 2000
Previous 47 346 2 1 5 5 1 4
Update 123 898 6 3 12 11 3 7
Increase 76 552 4 2 7 6 2 3
Year 2010
Previous 26 253 3 0 6 5 1 5
Update 58 628 9 1 14 13 3 8
Increase 32 375 6 1 8 8 2 3


Technical Documentation: Proposed Change in Population and Activity Factors for Lawn and Garden

Staff Contact:  Manuel Cordero Jr.


preload