The vehicles sector represents all direct CO₂ emissions generated by on-road transportation, including cars and trucks, within the boundary of interest. Emissions from vehicles represent where physical emissions from cars and trucks occur along roadways. Therefore, emissions from vehicles that are passing through a city on a highway will contribute to emissions for that city, even if those vehicles do not start or stop in that city. Crosswalk’s on-road emissions use GPS-based traffic data for the continental United States and average annual daily traffic data from the Federal Highway Administration (FHWA) for Alaska and Hawaii. Additionally, Crosswalk uses state-specific information from the FHWA about the vehicle fleet mix on different road classes and fuel economy for different vehicle types to estimate CO₂. Emissions are scaled in time using Energy Information Administration (EIA) fuel consumption data, U.S. Census population data, and OpenStreetMap data.

Emissions associated with powerplants are represented as emissions occurring at the location of the power plant, regardless of where the power is consumed. The power plant emissions data come from three sources: 1) EPA’s Clean Air Markets Division (CAMD) data generated from hourly measurements of CO₂ emissions from continuous emission monitoring systems (CEMS) stack monitoring, 2) EIA data on power plant fuel consumption reported at the monthly scale, and 3) U.S. Environmental Protection Agency (EPA) National Emissions Inventory (NEI) which captures some small co-generation facilities not included in the other data sources.

The residential buildings sector includes emissions from residences such as houses, apartments, and condominiums. The residential buildings sector represents direct emissions from residences, using data from the U.S. Environmental Protection Agency (EPA) National Emissions Inventory (NEI). Emissions are scaled in time using fuel data from the U.S. Energy Information Administration (EIA), and distributed to census block groups using building stock data from the National Structure Inventory (NSI). Emissions factors are used from sources including EPA and Intergovernmental Panel on Climate Change (IPCC).

This sector includes emissions from 16 different types of vehicles that do not typically drive on roads. These machines include lawnmowers, golf carts, construction equipment, and farming machinery. Data from the U.S. Environmental Protection Agency (EPA) National Emissions Inventory (NEI) are used to generate emissions estimates for this sector.

This sector includes emissions from airplanes and helicopters during taxi, takeoff, and landing, attributed to the city or town where the airport is located. Emissions from takeoff and landing include emissions from below 3,000 feet above ground level. This data is sourced from the Federal Aviation Administration Traffic Flow Management System Counts Data (TFMSC) for the largest 2,000 airports. For Airports not in TFMSC, aircraft activity is modeled using the Federal Aviation Administration Form 5010 Data. Emissions factors are used from the Intergovernmental Panel on Climate Change (IPCC). Airport equipment such as baggage carts are included in the mobile equipment category.

Industrial buildings emit CO₂ from combustion of fossil fuels in industrial processes such as manufacturing, oil and gas operations, refineries, and other heavy industry. Industrial sources are distinguished from commercial sources based on the Source Classification Code (SCC) used to report emissions in the U.S. Environmental Protection Agency (EPA) National Emissions Inventory (NEI). Data used to estimate emissions from industrial buildings includes data for both point sources (large facilities at fixed locations which are required by law to report their emissions to the EPA Greenhouse Gas Reporting Program (GHGRP), and non-point sources. Non-point sources are smaller facilities identified in the National Structure Inventory (NSI), which are not required by law to report their emissions to the NEI. Data come from the NEI and GHGRP, and emissions from non-point sources are scaled in time using State-level fuel consumption data from the U.S. Energy Information Administration (EIA). Emissions factors are used from sources including EPA and Intergovernmental Panel on Climate Change (IPCC).

Commercial buildings emissions are from buildings such as restaurants, office buildings, stores, schools, churches, libraries, hospitals, military installations, and other government buildings. Industrial sources are distinguished from commercial sources based on the Source Classification Code (SCC) used to report emissions in the U.S. Environmental Protection Agency (EPA) National Emissions Inventory (NEI). Data come from the NEI and are scaled in time using fuel data from the U.S. Energy Information Administration (EIA). Non-point buildings emissions are distributed to census block groups using building stock data from the National Structure Inventory (NSI). Emissions factors are used from sources including EPA and Intergovernmental Panel on Climate Change (IPCC).

For emissions from rail (passenger and freight trains), data from the U.S. Environmental Protection Agency (EPA) National Emissions Inventory (NEI) are used to generate emissions estimates.

For emissions from Commercial Marine Vessels, data from the U.S. Environmental Protection Agency (EPA) National Emissions Inventory (NEI) are used to generate emissions estimates.

Scope 2 emissions are accounted for at the location where purchased energy is consumed, rather than at the location where it is generated (e.g., at the location of a power plant). Scope 2 emissions are categorized into source sectors including residential buildings, commercial buildings, and industrial buildings. Buildings are differentiated by their classification in the National Structure Inventory (NSI). Scope 2 emissions (emissions from consumed electricity) are estimated for this sector for balancing authorities across the U.S. using the model published in "Tracking emissions in the US electricity system", by Jacques A. de Chalendar, John Taggart and Sally M. Benson. Proceedings of the National Academy of Sciences Dec 2019, 116 (51) 25497-25502. Emissions are distributed to census block groups using building stock data from the National Structure Inventory (NSI).