Off-Road Mobile Sources

Last updated September 9, 2019


Emissions from off-road sources were estimated using a suite of category-specific models or, where a new model was not available, the OFFROAD2007 model. Many of the newer models were developed to support recent regulations, including in-use off-road equipment, ocean-going vessels and others. The sections below summarize the updates made to specific off-road categories.

Ocean-Going Vessels (OGV)

CARB staff updated the OGV activity growth rates and NOx emission calculations in December 2016. These were based on 2014 data on vessel visits, 2014 data from the Ports of LA/LB on vessel power, and US EPA sources for emission rates. Growth factors are based on the Freight Analysis Framework. Additional information on CARB's general OGV methodology is available online for the 2019 update here - 2019 OGV Methodology or the 2014 update here - 2014 OGV Methodology

Cargo Handling Equipment (CHE)

The emissions inventory for the Cargo Handling Equipment category was updated to reflect new information on equipment population, activity, recessionary impacts on growth, and engine load in 2011. The information includes regulatory reporting data which provide an accounting of all the cargo handling equipment in the State including their model year, horsepower and activity. Background and supporting documents for the Cargo Handling Equipment Regulation are available here: Cargo Handling Equipment Regulation

Please Craft and Recreational Vehicles

A new model was developed in 2011 to estimate emissions from pleasure craft and recreational vehicles. In both cases, population, activity, and emission factors were re-assessed using new surveys, registration information, and emissions testing. Additional information is available at: Pleasure Craft and Recreational Vehicles

In-Use Off-Road Equipment

This category covers construction, industrial, mining, oil drilling, and ground support equipment. CARB developed this model in 2010 to support the analysis for amendments to the In-Use Off-Road Diesel Fueled Fleets Regulation. Population is based on reporting data, while activity, load and fuel use are based on survey data and statewide fuel estimates. In-Use Off-Road Equipment


The locomotive model is based primarily on population and activity data reported to CARB by the major rail lines for calendar year 2011. To estimate emissions, CARB used duty cycle, fuel consumption and activity data from the two main rail companies. Activity is forecasted for individual train types and is consistent with CARB's ocean-going vessel and truck growth rates. Fuel efficiency improvements are projected to follow Federal Railroad Association projections and turnover assumptions are consistent with U.S. EPA projections. The model was updated in 2016 with revised growth rates, and revised turnover assumptions. Additional information is available at: 2016 Revised Model
The additional locomotive categories (Switchers, Short Haul (Class III), Passenger) are all documented individually at Additional Locomotive Categories

Transport Refrigeration Units (TRU)

This model reflects updates to activity, population, growth and turn-over data, and emission factors developed to support the 2011 amendments to the Airborne Toxic Control Measure for In-Use Diesel-Fueled Transport Refrigeration Units. Additional information is available at: Transport Refrigeration Units

Fuel Storage and Handling

Emissions for fuel storage and handling were estimated using the OFFROAD2007 model. Additional information is available at: Fuel Storage and Handling

Diesel Agricultural Equipment

The inventory for agricultural diesel equipment (such as tractors, harvesters, combines, sprayers and others) was revised based on a voluntary survey of farmers, custom operators, and first processors conducted in 2009. The survey data, along with information from the 2007 USDA Farm Census, was used to revise almost every aspect of the agricultural inventory, including population, activity, age distribution, fuel use, and allocation. This updated inventory replaces general information on farm equipment in the United States with one specific to California farms and practices. The updated inventory was compared against other available data sources such as Board of Equalization fuel reports, USDA tractor populations and age, and Eastern Research Group tractor ages and activity, to ensure the results were reasonable and compared well against outside data sources. Agricultural growth rates through 2050 were developed through a contract with URS Corp. Additional information is available at: Diesel Agricultural Equipment