Emission factors

What are Emission Factors?

Emission factors are standardized coefficients that estimate the amount of greenhouse gases (GHGs) or air pollutants emitted per unit of activity, such as per kilometer driven, per liter of fuel consumed, or per tonne-kilometer transported. In road transportation, emission factors translate operational data into emissions, enabling carriers, shippers, and platforms to quantify and report their environmental impact consistently—and to power automated CO2 calculation in their TMS.

Detailed Explanation

At their core, emission factors link an activity (distance, fuel use, payload) to emissions for specific pollutants like CO2, CH4, and N2O, often expressed together as CO2e (carbon dioxide equivalent). They are derived from measurements, laboratory tests, and modeled data, and are published by recognized bodies. For trucking and van operations, emission factors can be defined:

• Per vehicle-kilometer (g CO2e/km), by vehicle and fuel type

• Per unit of fuel (kg CO2e/liter or MJ), reflecting combustion and upstream fuel production

• Per tonne-kilometer (g CO2e/tkm), incorporating load factor and backhauls

An important boundary choice is Tank-to-Wheel (TTW) versus Well-to-Wheel (WTW). TTW covers tailpipe emissions only; WTW adds upstream emissions from extracting, refining, and delivering fuel or electricity. Using TTW or WTW emission factors changes results and should be consistent with your reporting standard.

How Emission Factors Work in Road Transportation

In logistics, emission factors are applied to activity data to calculate emissions for routes, lanes, and accounts—the same variables leveraged by transport planning and dispatch to balance cost, distance, vehicle type, and load.

Factors vary by:

• Vehicle category and standard (e.g., van, rigid, tractor-trailer; Euro class)

• Energy type (diesel, biodiesel blends, CNG/LNG, HVO, electricity)

• Duty cycle and geography (urban, regional, highway; country-specific energy mix)

• Load and utilization (affecting per tkm results)

For combustion fuels, fuel-based emission factors are often the most accurate when high-quality fuel consumption data is available. Distance-based factors are useful when only mileage is known, while weight-based factors support multimodal comparisons and customer allocation. Practical levers that influence fuel use—such as driver behavior, idle time, and smoother site operations—are covered in depth in this guide to reducing the environmental impact of your supply chain.

Examples

• Distance-based example: A diesel 18-ton rigid truck runs 200 km with a factor of 750 g CO2e/km (WTW). Emissions = 200 × 0.75 = 150 kg CO2e.

• Fuel-based example: A tractor-trailer consumes 100 liters of diesel. With a WTW emission factor of 3.2 kg CO2e/liter, emissions = 100 × 3.2 = 320 kg CO2e.

• Tonne-kilometer example: A 10-ton payload moves 500 km with a factor of 90 g CO2e/tkm (WTW). tkm = 10 × 500 = 5,000 tkm. Emissions = 5,000 × 0.09 = 450 kg CO2e.

Tip: Electric freight vans use electricity-based emission factors (g CO2e/kWh). Results depend on the grid mix; country- or supplier-specific factors give more accuracy.

Key Benefits/Components

• Consistency and comparability: Emission factors standardize calculations across fleets, routes, and time periods.

• Scalability: Apply at shipment, lane, customer, or network level without changing methodology.

• Decision support: Compare fuels, vehicles, and routes to prioritize decarbonization (aerodynamics, driver training, alternative fuels, electrification).

• Compliance readiness: Align with common frameworks and customer reporting requirements using recognized factor sets.

• Transparency: Clear documentation of factor sources, boundaries (TTW/WTW), pollutants covered, and year of applicability.

Core components to define for any emission factor you use:

1. Boundary: TTW vs WTW and pollutants included (CO2, CH4, N2O, CO2e).

2. Unit: g/km, kg/liter, g/tkm, or g/kWh.

3. Vehicle and energy context: Vehicle class, Euro standard, fuel or electricity source.

4. Geography and year: Country-specific grid/fuel pathways; ensure the factor’s reference year matches your data.

5. Data quality: Source, methodology, and whether it reflects real-world duty cycles.

Industry Context

Emission factors sit at the heart of carbon accounting in road freight, underpinning customer emissions reports, Scope 1 and Scope 3 disclosures, tenders, and carbon surcharges. Shippers use them to compare carriers and modes; carriers use them to baseline performance, track improvements, and substantiate low-carbon services. Accurate emission factors also inform network design, consolidation strategies, and the business case for switching to HVO, LNG, or battery-electric vehicles. Site-level practices such as appointment scheduling, queue management, and faster turnarounds can also reduce fuel burn—see this overview of distribution center operations for context. To operationalize these calculations and share results with customers, teams can rely on integrated CO2 calculation workflows in their TMS.

Conclusion

Emission factors convert everyday transport activity into credible emissions data. Choosing the right boundary, unit, and level of detail—then applying current, geography- and vehicle-appropriate values—enables accurate reporting and better decarbonization decisions across road transportation, from transport planning and dispatch to automated CO2 calculations.