In many Catalan cities, changes are being made in the internal mobility of the City to improve environmental and acoustic quality. A well-known example for everyone is the creation of the Barcelona low-emission zone. But, did you know that in our city there is a project to create a zone with low emissions or a protected atmosphere? What does it mean and what does the creation of this area imply?

Currently, urban areas are densely populated and present high environmental and acoustic pollution, mainly due to the movement of vehicles within the City. According to data published on the website of the Green Revolution of the Terrassa City Council, the 50% of the air we breathe presents a pollution limit above the acceptable limits. These data and others can be found on the following page “Goodbye smoke and noise” ( The Terrassa Green Revolution is the name given to the new City model for improving mobility and quality of life for citizens.
This model, as established in the Sustainable Urban Mobility Plan 201-21  and the Air Quality Improvement Plan 2015-20 , not only implies the creation of a low emission area, but there will be modifications on the streets to balance public space between pedestrians, bicycles and public transport to favor the change in the dynamics of citizen mobility in our city.
These changes began in 2019 and will continue throughout 2020. One of these has been the change in circulation on Portal Nou street (Fig. 1).


Figure 1. Change of direction of the circulation of Portal Nou street. Source: Image taken from the document published on the Green Revolution website  of the Terrrassa City Council.
Thanks to the analysis of the data collected by the noise sensors located on the same street and comparing them with previous dates of the change, it was detected that there had been a decrease of almost 3% in noise compared to previous data (Fig. 2).

Figure 2. Compataion of noise after the circulation change with respect to that generated during the week and the previous year. Source: Data extracted from the analysis of the data captured by the sensor: Terrassa City Council.

If we look at the graph:

  • Bright blue color: corresponds to the data obtained during the week prior to the change in direction of circulation.
  • Off blue color: corresponds to the noise generated during the week following the change.

We can see that the change in direction has favored the improvement of the acoustic level, reducing noise almost 5 times compared to the previous week (remember that the noise level has a logarithmic scale and, you can consult the article “Measurement of the noise level” to know more). We can also perceive that the level of noise captured is homogeneous throughout the days without appreciating a difference in circulation on Saturday and Sunday.
The bright red and off charts have the same settings as the blue charts for the previous year (bright red for the week after the change and off red for the week before).
By implementing the changes foreseen in the Green Revolution, we hope to generate a protected atmosphere where citizens can enjoy better air quality and, thanks to the analysis of the data captured by sensors and meteorological stations distributed in the City, can confirm that the objectives marked in the Sustainable Urban Mobility Plan and in the Air Quality Improvement Plan are being fulfilled.


Bibliographic References:
• Terrassa City Council (2020). Goodbye smoke and noise! [online]. Available online:
• Terrassa City Council (2020). The green revolution [online]. Available online:
• Terrassa City Council (2020). Terrassa Air Quality Improvement Plan (2015-2020) [online]. Available online:
• Terrassa City Council (2020). Mobility plan [online]. Available online:

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