Massive characterisation of pollutant emissions produced by on-road traffic in Barcelona

In 2017 Opus carried out a major project to measure exhaust emissions from on-road traffic in the city of Barcelona and its metropolitan area. Opus RSE was contracted by Barcelona Regional, a public agency for urban planning led by Barcelona City Council. The other entities funding the project were RACC, Barcelona City Council and AMB (Àrea metropolitana de Barcelona)


This project has been one of the largest remote-sensing projects done in Europe and its results have pushed the city authorities to impose new restrictions on polluting vehicles.

Measuring emissions to create efficient policies

The levels of air pollutants in the city of Barcelona exceed the limit values recommended by the World Health Organization and established by the European Union. The city plans to tackle this health problem with the implementation of a package of measures aimed at reducing the average levels of NO2 and PM10 in Barcelona, which recorded an increase in the last two years (between 11 and 13%). 


The authorities hired Opus RSE to conduct an extensive and detailed analysis of the emissions, to truly understand their problem, the contribution of different types of vehicles to pollutant emissions and thus create efficient environmental policies.


 The Remote Sensing Devices were placed at 32 different locations in Barcelona. This mobility can only be achieved with Opus RSD AccuScan, which is small and easy to set-up.


The measurement sites represent important traffic areas inside and around the city of Barcelona, with the aim of making a representative characterisation of on-road traffic emissions throughout Barcelona: city center, motorways, port, urban accesses, industrial sites, etc.



Hundreds of thousands of vehicles were analyzed, so the understanding of traffic emissions in Barcelona is now very clear.


 It was particularly relevant finding that the average emissions of nitrogen oxides (NOx) from diesel passenger cars exceed the limits, including the most modern vehicles (Euro 6). It is true that, in general, all Euro 6 vehicles reduce their average emissions compared to older vehicles and come closer to meeting the limits set by European standards. However, it is very alarming that many Euro 6 vehicles fail to comply with emissions regulations. These vehicles were recently homologated, so it has been demonstrated once again that the real-driving emissions are much higher than those measured in laboratory type-approval tests.


The High Emitters of Barcelona, which account for 6% of the entire fleet, contribute between 20-30% of total traffic emissions. This group consists mainly of Euro 3 diesel passenger cars, but also 17% of relatively new passenger cars (Euro 5 and Euro 6) which would be inexpensive to repair (typically injection problems) and would immediately reduce emissions from road traffic.


The study showed that the identification and repair of High Emitters would be the most economical measure to reduce on-road traffic emissions.

Creation of Barcelona low emission zone

The results of the project helped to shape the current Low Emission Zone, which begins operations on 1 January 2020. Thanks to the information from the RSDs, the access rules will be quickly tightened up. The LEZ Barcelona/City environmental zone covers an area of around 92 km² in the municipality of Barcelona, so it will be one of the largest Low Emission Zones in Europe.

Updating of emission factors

Emissions inventories are important to cities' authorities. They allow them to estimate how much the different sources of pollution emit, the main one being road transport. There are commonly used emission factors, but they are generic and very outdated. In this project, the results were used to update these databases in order to have recent and more precise information on how much the vehicles circulating in Barcelona really pollute. Each city is different, and updating emission factors is a good and effective action. Thanks to having measured in so many different places, the information of this project was especially rich and complete.

Creation of accurate air dispersion models

Thanks to having measured in 32 different locations, real-world traffic emissions information is available in many diferent roads and streets of the metropolitan area, under a wide range of speed and acceleration.


This information is very valuable for air quality simulation models, as they take data from different sources and the more reliable they are, the more accurate the model's prediction is. The data from this project are used for simulations on the Marenostrum Supercomputer, one of the most powerful computing centers in Europe.


The prediction of air quality in Barcelona is now more accurate.

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