Vehicle CO2 data: WLTP, NEDC and regulatory compliance

Vehicle CO2 emissions are at the heart of automotive taxation in France and across Europe. Ecological penalties, company car tax, low-emission zones: regulatory decisions are based on this data. Understanding the measurement standards and knowing where to find reliable data is essential for every industry professional.

NEDC: the former protocol

The New European Driving Cycle (NEDC) was the standard for measuring emissions and fuel consumption in Europe from 1997 to 2018. This laboratory test protocol simulated an 11 km urban and extra-urban journey over approximately 20 minutes.

The problem with NEDC was its lack of realism. Test conditions were too favourable: ambient temperature of 20-30 degrees C, accessories switched off (air conditioning, headlights), optimised aerodynamics. NEDC values systematically underestimated real-world consumption and emissions, often by 20 to 40%.

WLTP: the current protocol

The Worldwide Harmonized Light-Duty Vehicles Test Procedure (WLTP) came into force on 1 September 2018 for all new models, then 1 September 2019 for all new vehicles. This protocol is significantly more rigorous and realistic:

• Test duration -- 30 minutes instead of 20, over a distance of 23 km
• Top speed -- 131 km/h instead of 120 km/h
• Four phases -- low, medium, high and extra-high speed (compared to two for NEDC)
• Options included -- the actual weight of the vehicle with its options is factored into the calculation
• Temperature -- tested at 23 degrees C with correction for 14 degrees C

As a result, WLTP values are generally 20 to 30% higher than NEDC values for the same vehicle. A vehicle rated at 120 g/km under NEDC may measure 145-155 g/km under WLTP.

Impact on French taxation

The ecological penalty

The ecological penalty (malus) is calculated from CO2 emissions measured under WLTP for new vehicles. The scale is progressive and changes each year. In 2026, the trigger threshold is set at a level that heavily penalises the highest-emitting vehicles. Access to accurate CO2 data is therefore essential to:

• Calculate the total acquisition cost of a new vehicle
• Inform customers about the applicable penalty amount
• Anticipate regulatory changes

Company car tax

The company car tax (formerly TVS, now the annual taxes on CO2 emissions and atmospheric pollutants) also uses CO2 values to determine the tax amount. Fleet managers need this data for every vehicle in their fleet to optimise fleet composition.

Low-emission zones (LEZ)

Low-emission zones use Crit'Air stickers, which are themselves based on the vehicle's Euro standard and fuel type. Although the Crit'Air classification does not directly rely on CO2, the complete technical data (Euro standard, fuel type) is needed to determine the applicable sticker.

How the API provides this data

The AutomotivAPI technical specs API returns CO2 data according to the standard applicable to the vehicle. For each vehicle, you get:

• CO2 emissions in g/km (WLTP and/or NEDC depending on the type-approval date)
• Combined, urban and extra-urban fuel consumption
• The Euro standard (Euro 6d, Euro 6d-TEMP, etc.)
• Fuel type and energy class

This data enables automatic calculation of the ecological penalty, company car tax and Crit'Air classification. For details on the technical specs API, see our dedicated guide.

To understand how regulations govern access to this data, read our article on vehicle data regulations in France and Europe.