Computer model to calculate emissions from road traffic

COPERT calculates emissions and energy consumption from road transport. The main purpose of the model is to facilitate national experts to compile their emissions inventory, but the scope of the model goes beyond that. COPERT can be used as a policy assessment tool for any type of environmental studies. The model can also act as a reference point for researchers to find information on the emission and energy consumption levels of any type of new vehicles existing on the European roads but also older vehicle technologies which might still exist.

The model consists of 3 main sections, the input section, the emission factor section, and the results section where the calculated emissions are presented. Estimated emissions are grouped in three sources: Emissions produced during thermally stabilized engine operation (hot emissions), emissions occurring during engine start from ambient temperature (cold-start and warming-up effects) and NMVOC emissions due to fuel evaporation. Non-exhaust PM emissions from tyre and break wear are also included. The total emissions are calculated as a product of activity data provided by the user and speed-dependent emission factors calculated by the software. The spatial scale of the model can range from a street to continental level. The temporal extend of COPERT can also range from annual to multi-annual, although it actually depends on the activity data provided. This means that the calculation period can range from one week to a number of years.

COPERT can be used for policy anticipation, implementation and evaluation for air quality related policies. It can be used for trend analysis, and input for air quality modelling and impact assessment studies, either directly or after some modifications, sometimes in combination with other emission models. It has been recently used for the assessment of the upcoming Euro 5 emission standards for the L-category vehicles, and the revised type approval procedure for evaporation emissions from Euro 6 vehicles.

COPERT applies EEA’s EMEP/EEA air pollutant emission inventory guidebook version 2016, and more specifically chapter 1.A.3.b.i-iv Road transport 2017. The model structure is split in three parts, input, emission factor calculation and results.

Inputs: for each of the 373 vehicle categories (137 cars, 54 vans, 99 trucks, 47 busses, 36 motorcycles) divided per load capacity (trucks & busses) of engine capacity (other vehicles), Euro emission standard, fuel type:

• Population
• Mileage
• Lifetime cumulative activity
• Average speed in urban/rural/highway streets
• Share of km run in urban/rural/highway streets
• Load factor and road slope for trucks and busses
• Size of tank and canister (for the evaporative part of the emissions only)
• Percentage of evaporation in urban/rural/highway streets (for the evaporative part of the emissions only)

For the environmental conditions:

• Minimum and maximum monthly average temperature (for the evaporative part of the emissions only)
• Humidity (for the impact of the A/C use)

For each fuel type:

• The content of metals in the fuel
• The ration of hydrogen to carbon and oxygen to carbon
• Heavy metal content
• Density
• Fuel energy content

Parametrisations: The model contains a dataset of emission factors (grams of pollutants per kilometre and energy consumption per kilometre) derived from measurements. for urban/rural/highway operations. Depending on the input vehicle speed, the model calculates the appropriate emission or energy consumption factor. Using the vehicle population, mileage and share of kilometres driven in each road type the model calculates the total emissions and energy consumption. If more detailed information is available the user can provide his own emission factors to be used for the calculation of emissions.

The model also contains parametrisations for simulating additional CO2 emissions due to:

• using the air condition
• lube oil consumption using different SCR rates (an abaitment technology for NOx)

or improve emission calculation for NOx, CO and VOC by taking into account the vehicle age.

CO2 emission calculation can be further improved by providing information on the type approval CO2 for passenger cars.

If statistics on the energy/fuel consumption (sales) are provided as input to the model, the emissions are rescaled and adjusted to reach consistency.