madrid central
Is regulating car access in downtown areas effective for our beloved Earth?
Social Data Analysis & Vizualisation, DTU | Spring, 2022
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Social Data Analysis & Vizualisation, DTU | Spring, 2022
FIGURE 1 - CENTRAL MADRID DELIMITATION
30th November 2018 - Madrid, Spain.
A drastic environment measure enters in force in the Spanish capital.
With IPCC [Intergovernmental Panel on Climate Change] reports getting more and more alarming over the past few years, environmental questions became at the heart of urban policies.
Besides, based on European Environment Agency conclusions, air pollution put the health of citizens at risk, being the "major cause of premature death and disease".
To reduce pollution, the City Council of Madrid decided to establish a low-emission zone called "Madrid Central" in the city center. With a few exceptions, all polluting vehicles were forbidden in "Centro", the central district of Madrid.
The regulation was expected to cut NO2 emission by 40% in this district, by reducing traffic. It aimed to make the city more sustainable and to dedicate streets to pedestrians. Unfortunately, it was truncated because of political and economic reasons, rather than environmental ones...
In this study, we aim to evaluate the effectiveness of this vehicle regulation on pollution by analyzing traffic and air quality data.
Introduction
Introduction
Madrid
Madrid
Madrid, the capital of Spain, has a metropolitan area population of about 6.7 million inhabitants, making it the second-largest European city - right after Berlin.
Madrid is administratively divided into 21 districts, with "Centro" as the central district, where the vehicle regulation took effect.
INTERACTIVE MAP 1 - DISTRICTS OF MADRIDHover to get district's name
Madrid Central in 4 key dates
Madrid Central in 4 key dates
30th Nov. 2018
Inauguration
15th March 2019
Fines are applied
1st July 2019
The End
11 Dec. 2021
Switch to Madrid 360
It consisted of 30 measures, among which we can highlight: Central Area Zero Emissions, reform of the main access roads to the center, regulation of parking with air quality criteria, and expansion and renewal of the bus fleet.
Madrid Central did not impose fines to combustion car drivers from day one. There was a transition period when no traffic tickets were given to drivers that entered this district. It was since the 15th of March 2019, when any vehicle that was not allowed to enter the area of Madrid Central risked getting a traffic ticket, with a fine of 90€.
After council elections, the new Madrid's government announced on the 15th of June 2019 that they will impose a moratorium on the Madrid Central fines protocol. Giving Madrid the dishonor of being the first major European city to back down from a measure to limit polluting emissions... From the 1st of July 2019, no more fines were imposed to drivers.
Eventually, the new government rectified, and proposed a much less drastic and restrictive measure, that entered into force on the 22nd of September 2021, and that began to issue fines again from the 11th of November 2021. This measure was considered as a regression of the previous one by the Ombudsman (defender of the population)
Focus on Data
Focus on Data
Note: for not being biased by the effect of COVID lockdown situation, we will restrict our analysis period up to February 2020.
Air Quality
Air Quality
For European standard compliance, cities installed air quality stations in various places to monitor polluting gas in urban areas.
Madrid counts 24 stations across the city, and one of them is located in Plaza del Carmen, in the middle of the Madrid Central area.
In this study, we evaluate the border effect of vehicle regulation by exploring air quality around the low-emission zone. For this purpose, we selected 4 stations that surround the Madrid Central area: Plaza de España, Castellana, Retiro and Méndez Álvaro.
We also want to get an air quality baseline with the data of stations that are far from Madrid Central area. Thus, the 4 remote stations that we will inspect here are: El Pardo, Barajas Pueblo, Villaverde and Ensanche de Vallecas.
INTERACTIVE MAP 2 - AIR QUALITY STATIONS IN MADRIDHover to get station's name and corresponding monitored gases
HOW HAVE GAS CONCENTRATIONS CHANGED OVER TIME?
Air quality stations monitor various gas concentrations each hour in Madrid that we can compare in the following interactive line chart.
A positive percentage refers to a gas concentration increase in comparison with the same month of the previous year. In contrast, a negative percentage refers to a gas concentration drop in comparison with the same month of the previous year, which is the aim of Madrid Central.
INTERACTIVE CHART 1 - COMPARISONS OF GASES WITH THE MONTH OF PREVIOUS YEARHover data points to get the precise month and the precise concentration's percentage evolution | Click on legend items to hide some parts of the dataThe gray dashed lines represent the 3 key dates (start of Madrid Central, start of fines, end of Madrid Central)The thin horizontal red line at 0% means that the gas concentration remains the same
What do we observe?
Inside the low-emission zone of Madrid Central (first tab), the vehicle regulation leads to a decrease or a slower increase of Nitrogen Oxides (NOx = NO2 + NO), Ozone (O3) and Sulfur Dioxide (SO2). These gases are three common pollutants emitted by cars that are highly involved in air pollution.
Nonetheless, air pollution outside Madrid Central - both near and far from the low-emission zone borders, starts to decrease when fines are enforced only.
INTERACTIVE MAP 3 - ANIMATED MAP FOR NO2 CONCENTRATIONS FOR EACH STATION OVER TIMEGreen = below European standard / Red = above European standardClick on a circle to get station's name
WHAT ABOUT EUROPEAN AIR QUALITY STANDARDS?
In the animated Interactive Map 3, it can be seen that Madrid experienced periods of high pollution before the implementation of Madrid Central, e.g. from 2016 to 2018.
Then, after a short transition time of some months, NO2-based air pollution remains below European standards thanks to Madrid Central.
Eventually, air pollution becomes critical again as soon as Madrid Central ends.
A SYNTHESIS OVERVIEW OF THE MADRID CENTRAL EFFECT ON AIR POLLUTION
First, this multi-bars chart allows us to reproduce the results of a previous study that has been conducted on the same subject.
Indeed, Enrique Galdon-Sanchez et al. states that "the concentration of nitrogen dioxide (NO2), a harmful pollutant, decreased by 18.6% in the Madrid Central area". We also found the same drop percentage, with a NO2 concentration from 46.36 µg/m3 to 37.71 µg/m3. Since the European standard for NO2 concentration is 40 µg/m3, Madrid Central operation actually helped the city to stop exceeding the limit.
According to the same research paper, there is almost no border effect, since the NO2 air pollution outside Madrid Central had only a 3, increase during the vehicle regulation. We end up to the same conclusion as well.
INTERACTIVE CHART 2 - AVERAGE CONCENTRATIONS OVER THE MADRID CENTRAL PROCESS IN DIFFERENT LOCATIONSHover the bar to get the exact gas concentration value
In addition, we get a bit more in details since we split the Madrid Central into 2 periods: before and after fines enforcement. We clearly see that a low-emission zone becomes really efficient after fines enforcement, e.g. when citizens risk paying if they drive in the central district!
We also notice that not only the pollution of the central district, but the pollution of ALL Madrid districts, decreased after the application of fines. Given this observation, we can wonder whether this global trend of air pollution decrease in the city is related to weather condition rather than Madrid Central regulation. In fact, rains clean air pollution. However, according to an advanced scientific study on weather, the period of Madrid Central was not that rainy. Thus, the air pollution decrease is not weather-related, so it seems that Madrid Central had a positive effect on the whole city actually!
Besides, we show that ending Madrid Central by lifting the restrictions and authorizing vehicles back in the city center leads to a resurgence of NO2 pollution and a concentration that exceeds the European limit again...
Traffic
Traffic
Madrid counts with more than 4000 traffic measurement points, from which we use 3886 stations, where 176 are located inside Madrid Central area.
Using the data measured in these stations allow us to analyze changes of traffic before and the Madrid Central active period.
We are going to focus on one specific measure: the traffic intensity, which informs on how many vehicles are recorded in a traffic measurement station in a 15 minutes period, using vehicles per hour as unit.
INTERACTIVE MAP 4 - TRAFFIC MEASUREMENT STATIONS IN MADRIDHover to get the name of traffic measurement stations and the district where it belongs | Click on legend items to mute data
HOW HAS TRAFFIC CHANGED IN MADRID CENTRAL AREA?
INTERACTIVE MAP 5 - AVERAGE TRAFFIC INTENSITY PER STATION BEFORE (LEFT) AND DURING (RIGHT) MADRID CENTRALHover on traffic points to get more details
To see if the Madrid Central measure was effective, it is not enough to analyze the air quality. We also have to see if the traffic intensity decreased. For this purpose, we display the average of traffic intensity before and during the application period of this measure.
From what we see in the Interactive Map 5, it seems that the measure was efficient.
We can appreciate changes, especially in the area of Gran Vía, the long northern road that crosses the district from East to West. Many points turned into a more bluish tone, which means lower traffic.
In Interactive Map 6, we can notice these changes much better, as we display the difference of traffic between before and during. Based on this map, it seems that the Central Madrid measure was effective and reduced the amount of vehicles in the city center.
But we do not know yet if this is a real difference, or if it is just that in this period of time there was less traffic in all of Madrid... We need to do a further analysis to confirm that!
INTERACTIVE MAP 6 - DIFFERENCE OF TRAFFIC INTENSITIES PER STATION BEFORE AND DURING MADRID CENTRALHover to get details
HOW HAS TRAFFIC INSIDE MADRID CENTRAL AREA CHANGED IN COMPARISON WITH THE TRAFFIC OUTSIDE?
In order to really see if there was a change in the traffic intensity while Madrid Central was applied, we compare before and during it, but we also make the comparison between the traffic inside and outside Madrid Central.
Weekly Analysis
Let's first analyze how people in Madrid use their vehicles through the week, to get some insights and detect if there is any noticeable change during Madrid Central. From both charts we can see that there is more traffic during the weekdays, both in and out of Madrid Central, increasing from Monday to Friday, and dropping on the weekends.
What is interesting and noticeable thanks to the Interactive Chart 3, we can see how the Madrid Central area has more average traffic compared with the others districts before the measure was imposed.
However, during its active period, the average of traffic intensity decreases in Madrid Central area, compared with the other districts. We can observe this from the first plot of Interactive Chart 4, as the bars during the week are lower than the line. Also, from the lollipop plot we clearly see that all the points have moved to the right, meaning there is a much fewer cars inside the Madrid Central area than the other districts.
This may be an clue that the Madrid Central measure was effective in reducing the traffic compared to the average in the city.
INTERACTIVE CHART 3 - WEEKLY ANALYSIS BEFORE MADRID CENTRALHover to get details
INTERACTIVE CHART 4 - WEEKLY ANALYSIS DURING MADRID CENTRALHover to get details
Monthly Analysis
Now we analyze the traffic behavior during the different months of the year inside and outside Madrid Central area. In Interactive Chart 5, we are interested in seeing how the traffic changes during the different years.
To do so, we calculate the difference of the average of traffic between inside and outside the Madrid Central area to see what happens. We discover that in 2018 and 2019, this difference gets smaller.
INTERACTIVE CHART 5 - DIFFERENCE OF AVERAGES OF TRAFFIC INTENSITY IN AND OUT OF MADRID CENTRALHover to get details | Click on legend items to hide dataThe thin horizontal red line represents equal number of traffic inside and outside Madrid Central
INTERACTIVE CHART 6 - MONTHLY ANALYSIS OF MADRID CENTRAL TRAFFICHover to get details | Click on legend items to hide dataThe gray dashed lines represent the 3 key dates (start of Madrid Central, start of fines, end of Madrid Central)
Finally, we can compare the whole timeline of inside and outside Madrid Central. Interactive Chart 6 allows us to compare the traffic intensity change over time, and we can see a change when the measure enters into force. We observe that after it started, Madrid Central changes from having an average over the city, to having slightly less traffic than the average in the city.
With all these data analysis and visualizations, we verify that the measure was effective in reducing the amount of traffic inside Madrid Central, as there is a significative change and difference before and after the implementation of the measures in the "Centro" district of Madrid.
Relation between air quality and traffic
Relation between air quality and traffic
Once we have analyzed both air quality and traffic, each on their own, we want to know if the traffic reduction is related to the improvement of the air quality. One of the main ideas behind Madrid Central was to reduce traffic in an attempt to get better air quality, thus we want to check if this is true.
For this purpose, we calculate the correlation matrix between traffic and each of the pollutants.
The matrices do not seem to indicate that there is a correlation between traffic and air quality inside Madrid Central, either before, during and in the city of Madrid as a whole. In the city of Madrid, we find a big correlation between different gases (CO-NO2, CO-O3, NO2-O3), but we do not see any of them being strongly related to traffic.
If we focus only on Madrid Central, the correlation is even lower, and it does not change much before and during the measure. We even lose the correlation between the different gases, which seems odd.
FIGURE 2 - CORRELATION MATRIX BETWEEN TRAFFIC AND EACH GAS
These results indicate that a direct relationship between traffic and air quality cannot be found, and therefore, there may be additional parameters that are not taken into consideration, such as rain, wind, or pollution from other sources such as industries, boilers or livestock.
End of the story
End of the story
In the light of this Madrid Central study case, we investigated whether the implementation of vehicle regulations in dense urban areas contributes to reducing pollution.
To recall our primary question: WAS MADRID CENTRAL EFFICIENT AS EXPECTED?
The answer is YES!
Regarding both air quality and traffic data, we show that Madrid Central was efficient. The NO2 concentration decreased by 18.6%, and it decreases especially after the enforcement of fines for drivers. This way, Madrid ended below the European standard of NO2 as required. Traffic also decreased during the implementation period of Madrid Central, and it even gets below the traffic that is observed outside the low-emission area.
Nevertheless, based on the correlation matrices we computed, air quality and traffic don't seem very correlated. Even though they are positively correlated, the correlation coefficients are lower than expected intuitively. A part of the explanation may rely on the fact that air pollution depends on many more factors than traffic: it is related to urban life, surrounding buildings, weather or people behaviors for instance.
Finally, as you know, Madrid Central regulation has been lifted due to a political reversal... We show in our study that allowing cars back in the city center lead to a return to the original pollution situation.
The current Council of Madrid is in transition to apply their new environmental plan called MADRID 360.
MADRID 360 is a much more ambitious measure, but with a long-term staging, and far less restrictive than Madrid Central. It allows more vehicles inside the city center, has more parking spots, etc. It will increase the area of considered limitations zone year by year, in an attempt to reduce the traffic further, and hopefully it will.
As a summary, MADRID 360 has fewer restrictions on vehicles, but covers a much greater area.
Stay tuned, and let's hope this new plan will be effective enough, for the sake of the health of our dear Earth!
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