9.6 Off Road Motorcycles & All Terrain Vehicles
Categories 1763 - 1768
9.6.1 Introduction
Categories 1763 through 1768 are used to inventory exhaust emissions (NOx, CO, PM, PM10, PM2.5, ROG, SO2, and TOG) from off-road motorcycles, all-terrain vehicles (ATV), minibikes, golf carts, specialty vehicles, and snowmobiles, respectively.
9.6.2 Methodologies
The Off Road Motorcycles & All Terrain Vehicles emissions are derived by California Air Resources Board (CARB) inventory staff. This significant emissions dataset, sorted by county, is published every few years and is a product of the State Implementation Plan (SIP) emissions document formally known as the California Emissions Projection Analysis Model (CEPAM) inventory. BAAQMD staff export the emissions data directly from CEPAM into the District’s Base Year inventory package. This calculation approach and collection of categories are internally termed as “CARB Source Categories”.
This base year inventory uses the 2016 CEPAMv1.05352 to estimate emissions from “CARB Source Categories”. This version of the CEPAM derives emissions from a 2012 base year inventory and contains backcasts and forecasts from year-2000 to year-2035. All applicable regulatory and technological controls are assumed to be built into the CEPAM dataset during CARB staff’s inventory computation work. After the emissions data are exported, the inventory for CARB Source categories is taken through a quality assurance (QA) process.
9.6.3 Changes in Methodology
Emissions data were obtained from the CARB’s 2016 CEPAMv1.051. In comparison, the emissions in the previous inventory methodology involved area source categories derived from the CARB’s OFFROAD2007 model.
CARB regulation in effect in 2000 stated that Districts were not in attainment of the Federal one-hour Ozone standard could not allow purchase of gasoline-powered golf carts off-road vehicles. Since BAAQMD was not in attainment, the Air District was subject to this rule and emissions from these vehicles decreased through time. The CARB Off-road Golf carts (cat_id 1766) historical emission data were retained in current emission inventory.
9.6.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
9.6.5 Trends
(a) Historical Emissions / History
California Air Research Board (CARB) developed an off-road vehicle emission inventory (OFFROAD2007) model to estimate emissions from off-road motor vehicles for all counties and air basins in California. The OFFROAD model contains a comprehensive list of equipment from a wider range of categories. Historical emissions for Off Road Motorcycles & All Terrain Vehicles were estimated based on the CARB’s Off-road vehicle emission inventory model. The previous inventory’s criteria air pollutants and GHG emissions data in the Bay Area were obtained from the CARB’s OFFROAD2007 model.
Three different methods are used for backcasting to project historical emissions prior to year-2000 going back to year-1990, which is the starting year of the current base year inventory (referred to as BY2015). Following preliminary evaluation of the data available for initial years (post-year 2000) in the CEPAM inventory, BAAQMD staff recommends a backcasting approach. The default backcasting approach is defined by a formula here –
\[ \begin{eqnarray} \text{BY2015 emissions for year X for county Y} = \text{BY2011 total emissions for year X} \\ \\ \times \dfrac{\text{BY2015 year-2000 emissions}}{\text{ BY2011 year-2000 emissions}} \\ \\ \times \dfrac{\text{county Y fraction}}{\text{ fractional total}} \end{eqnarray} \]
This calculation is referred to as the BY2011 scaling method (based on the previous base year inventory). The second calculation approach is to derive the linear regression best fit of the year 2000-2008 CARB Sources emissions data for a category, species, and county, and extrapolate that data back in time. If this backcasting results in negative emissions prior to a certain year, the lowest positive emission value is held constant from that particular year back to year-1990. The third possible calculation approach is to use a specific growth profile for the category, provided by the in-house staff expert. These custom growth profiles are often derived from surrogate data provided by another agency or resource, or available activity data that is assumed to scale with the emissions for that specific CARB Source category.
For the off-road motorcycle and ATV categories, the BY2011 scaling method is used to derive emissions for years 1990 through 1999.
(b) Future Projections / Growth
Emissions forecasting was done by holding the year-2035 emissions data constant through and up to year-2040. For CARB Sources, emissions are forecasted by CARB staff by applying growth profiles to the base year-2012 inventory data (see above in ‘Methodology’ section).
(c) Control
Emissions include expected benefits from CARB’s Re-Formulated Gasoline Phase I and Phase II (1992 and 1996 respectively) and Off-Road Recreational Vehicles Regulations beginning 1997.
9.6.6 Uncertainties
The estimated Off Road Motorcycles & All Terrain Vehicles emissions for Solano and Sonoma counties under District’s jurisdiction may contribute to an increased uncertainty of the Bay Area Off Road emissions.
9.6.7 Contact
Author: Michael Nguyen
Reviewer: Sukarn Claire
Last Update: November 06, 2023
9.6.8 References & Footnotes
CARB. 2016. California Emissions Projection Analysis Model (CEPAM) inventory, https://www.arb.ca.gov/app/emsinv/2016ozsip/2016ozsip/fcemssumcat_2016o3sip105.php↩︎