Descrizione 1
Antonella Bernetti
Stricter emission standards, the introduction of new technologies into the market—such as the installation of catalytic converters in vehicles—and improvements in fuel quality have led to significant reductions in the specific emissions of various pollutants from passenger cars and trucks; however, these improvements have been partially offset by the increase in traffic.
Specific emissions of NMVOC, NOₓ and PM refer to the emissions of the mentioned pollutants from a passenger car, estimated with reference to the vehicle’s actual on-road performance and expressed as mass emissions per kilometre travelled. The emission factors shown represent national averages, obtained by dividing total emissions by total mileage. These indicators are linked to the UNECE Convention on Long-range Transboundary Air Pollution (CLRTAP) and to urban air quality. They refer only to passenger traffic, specifically to road passenger cars. These emissions are influenced by vehicle technology and engine size, the energy efficiency of the engine, the fuels used by the circulating fleet (number and type of vehicles), vehicle usage (occupancy rates and load factors), and driving characteristics (speed and driving style).
To quantify and compare the emission factors of different pollutants for passenger cars using different types of fuel.
At the EU level, pollutant emissions from light-duty road vehicles are regulated with reference to passenger cars and light commercial vehicles. Among the most recent standards, Euro 5 and Euro 6 were adopted in 2007, becoming mandatory in January 2011 and September 2015, respectively, for the type approval and registration of new vehicle types. In particular, the Euro 6 standard introduces further significant reductions in nitrogen oxide emissions per kilometre for diesel vehicles. The European regulatory framework concerning the Euro 6 standard represents an evolution in the tightening of limits on pollutant emissions from vehicles and is structured in various phases:
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Euro 6A, mandatory for vehicles registered from January 2016
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Euro 6B, which differs from 6A with further reductions in particulate emissions
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Euro 6C, mandatory for all new cars sold from September 2018 and for those type-approved from September 2017
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Euro 6 Temp, mandatory for all new cars sold from September 2019 and those approved from September 2018
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Euro 6D, mandatory for all registrations from January 2021 and type approvals from January 2020
Starting from September 2017, the WLTP (Worldwide harmonized Light vehicles Test Procedure) was introduced, accompanied by the RDE (Real Driving Emissions) test, which provides a more realistic representation of a vehicle’s actual on-road emissions compared to the previous NEDC (New European Driving Cycle), which was the former EU standard.
Descrizione 2
EMEP/EEA air pollutant emission inventory guidebook 2023, EEA Report No 06/2023 (https://www.eea.europa.eu/publications/emep-eea-guidebook-2023)
ISPRA, Italian Emission Inventory 1990 – 2022, Informative Inventory Report 2024, Istituto Superiore per la Protezione e la Ricerca Ambientale, Rapporti 400/2024
It should be taken into account that the estimated emission factors represent the current state of methodological advancement, with reference to the available measurements for each vehicle category and fuel type.
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Qualificazione dati
ISPRA, the database of average emission factors for road transport in Italy, 2024 https://fetransp.isprambiente.it/#/
National
2022
Qualificazione indicatore
The indicator is based on estimates produced using complex algorithms and derived from data provided by the National Emission Inventory. It is representative of average performance at the national level.
When applied to pollution estimation in specific territorial contexts (e.g., urban traffic), the level of uncertainty may increase, as emissions are also influenced by driving styles and actual vehicle usage conditions. Nevertheless, it represents the best available estimate at the national scale.
The state assessment receives a poor rating primarily due to persistent emission-related issues in the transport sector, its significant contribution to total national emissions for many pollutants, and the ongoing discrepancies between type-approval emission values and those actually measured under real-world driving conditions. The analysis of on-road emission factors shows that diesel-powered vehicles exhibit the highest levels of nitrogen oxides (NOₓ) (0.46 g/km) and exhaust particulate matter (PM) (0.01 g/km), while gasoline-powered vehicles are characterized by the highest emission factors for non-methane volatile organic compounds (NMVOCs) (0.40 g/km).
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Dati
Figure 1: Average on-road nitrogen oxides (NOx) emission factors for passenger cars (2022)
ISPRA
The data are derived from the National Emission Inventory 1990-2022 compiled by ISPRA.
Figure 2: Average non-methane volatile organic compound (NMVOC) emission factors for road passenger vehicles (2022)
ISPRA
The data are derived from the National Emission Inventory 1990 – 2022 compiled by ISPRA.
Figure 3: Average exhaust particulate matter (PM) emission factors for road passenger cars (2022)
ISPRA
The data are derived from the National Emission Inventory 1990 – 2022 compiled by ISPRA.
Environmental impacts of mobility include direct effects on human health related to the emission of substances harmful to humans, with direct pathogenic effects. The transport sector constitutes a determining sector in atmospheric pollutant emissions, such as: NOx - Nitrogen oxides; NMVOC - Non-Methane Volatile Organic Compounds; PM - Particulate Matter.
In Italy, harmful emissions produced by road transport have decreased significantly in recent years (see indicator "Atmospheric pollutant emissions from transport"), thanks to the introduction of catalytic converters, fine particulate filters and other technologies installed on vehicles, such as canisters aimed at reducing evaporative emissions.
Polluting emissions are generated both during vehicle use (direct Tank-To-Wheel emissions) and during fuel production (Well-To-Tank emissions). For the first category, analyses and measurements are performed directly on vehicles. For the second, system studies and evaluations are considered, which include the production chains of different fuels (extraction, transport, refining, distribution).
Emissions during use are monitored by ISPRA, which has created and annually updates a database of average emission factors related to road transport. This database is linked to the preparation of the Italian Emission Inventory, aimed at verifying the international commitments on atmospheric environmental protection.
The emission factors published in the database form the basis for estimates of emissions and average national consumption related to road transport obtained through the application of the COPERT 5 model (2022 update of the National Emission Inventory reported in 2024; the references used are the IPCC Guidelines for greenhouse gases and the EMEP/EEA Guidebook for atmospheric pollutants).
Discrepancies exist between type-approval data and data related to actual on-road vehicle performance. The emission and consumption factors reported in the database are estimated with reference to real driving conditions that also consider results of experimental measurements performed on vehicles.
In the evaluations related to gasoline, diesel, and natural gas, the respective shares of biofuels are included. Separately for each pollutant: Nitrogen oxides, Non-Methane Volatile Organic Compounds and Particulate Matter at the tailpipe, the average emission factors per km traveled by passenger cars with different fuel types (gasoline, gasoline-electric hybrid, diesel, PHEV diesel-electric hybrid, LPG and natural gas; BEV electric passenger cars with zero tailpipe emissions are also reported) are compared.
The reference is to the national passenger car fleet in circulation as of December 31, 2022, averaged across different engine displacement classes and Euro standards. In the development of the estimates, specific national measurements on emission factors for LPG-fueled passenger cars (for Euro 6 a/b/c and Euro 6 d-temp cars) and measurements concerning natural gas-fueled passenger cars (Euro 4, Euro 5, Euro 6 a/b/c, Euro 6 d-temp) were integrated.
Regarding nitrogen oxides, the comparison between emission factors shows how diesel is characterized by significantly higher NOx values compared to other fuels. Lower is the emission factor value of gasoline passenger cars. Markedly lower are the emission factor values for LPG, PHEV diesel-electric, compressed natural gas, gasoline-electric hybrids, which show progressively decreasing values (Figure 1).
Regarding Non-Methane Volatile Organic Compounds, the comparison between emission factors highlights very high values for gasoline vehicles, followed at a distance by LPG, gasoline hybrids and natural gas, much lower are the emission factors of diesel engines and in particular diesel hybrids (Figure 2).
Regarding Particulate Matter at the tailpipe, the comparison between emission factors indicates how diesel presents significantly higher values compared to other fuel types (Figure 3).