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Category Archives: Sustainability

The “moles” digging the M6 metro: how a TBM builds the tunnel, ring by ring

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The “moles” of Metro Line 6 dig the earth, bring it to the surface and raise the tunnel behind them, almost simultaneously. Their technical name is TBM, from Tunnel Boring Machine.

The TBMs “Sfânta Maria” and “Sfânta Ana”, which are working on the South Section of Metro Line 6, weigh around 600 tonnes and have cutterheads roughly 6.60 metres in diameter. In length, they come close to a football pitch. They enter the ground, and behind them they leave a circular, reinforced tunnel, ready for the next stages.

At the front is the cutterhead, a huge metal disc fitted with cutting tools. It rotates, breaks up the ground and pushes the material into a chamber where the pressure is controlled at all times. The pressure keeps the excavation face stable and allows the machine to advance under control. From there, the material travels onto a screw conveyor, then onto conveyor belts, and out of the tunnel. It is loaded up and taken to authorised sites.

While digging goes on at the front, the tunnel is already being assembled behind the shield.

Segments and tunnel rings

The TBM advances using hydraulic rams that push against the last ring installed. After each advance, a device called an erector lifts the segments, the precast concrete elements, and sets them side by side until a new ring is closed. A gap remains between the concrete ring and the ground, which is filled by injecting a special grout known as bentonite. The operation fixes the structure in place and helps stabilise the surrounding ground.

Then the cycle begins again: excavate, remove the material, advance the machine, install a ring, inject the grout. And so it goes, a few metres a day, month after month.

How the “mole” knows where to go

Tens of metres underground, orientation has nothing to do with instinct. The TBM has guidance systems, sensors and survey reference points tied to the project coordinates. The operators follow the alignment constantly and can correct the direction with very fine adjustments. From the control cabin they monitor, in real time, the pressure in the excavation chamber, the amount of material extracted and the position of the machine relative to the designed axis. To these are added the operating parameters of the cutterhead and of the hydraulic systems, plus the ring-building operations.

Under normal conditions, the TBMs on the South Section of Metro Line 6 in Bucharest advance on average by about 1.5 metres per hour. That sounds like very little, until you look at what happens in that hour: the machine excavates around 60 cubic metres of material and prepares the installation of the tunnel’s permanent structure.

In 24 hours, an average of 13 to 14 rings are installed. The teams work in three shifts and the activity is continuous, with the stoppages needed for checks and maintenance. The pace varies according to the ground, the recorded parameters and the maintenance work.

Romania’s “moles”: from the metro to tunnels through the mountains

TBM technology is not being used in Romania for the first time. On Metro Line 5 in Bucharest, the excavation was carried out by “Sfânta Varvara” and “Sfânta Filofteia”.

On the Brașov–Sighișoara railway line, on the Apața–Cața subsection, four TBMs are at work, “Eleni”, “Varvara”, “Alexandra” and “Konstantina”, on the Ormeniș and Homorod twin tunnels. The railway machines have a different diameter and work in different geological conditions, but the principle is the same: controlled excavation, removal of the material, immediate installation of the structure and monitoring of the parameters.

The names follow a long tradition in tunnelling projects. Saint Barbara is regarded as the protector of miners and of those who work underground. On Metro Line 6, the tradition continues with “Sfânta Maria” and “Sfânta Ana”.

What happens at the surface

Although the activity takes place underground, the operation of the TBM is backed by an extensive monitoring system. The pressure in the excavation chamber, the amount of material extracted, the route of the machine and the behaviour of the ground are checked at all times. In the areas within the zone of influence of the works, special equipment is used to monitor the ground and the buildings.

The underground route to the airport

Metro Line 6 will have 14.2 kilometres of double track and 12 stations, and will create the first direct metro connection between Gara de Nord and Henri Coandă International Airport.

The video shows how the machine advances and how the concrete segments become, ring by ring, the structure of the future tunnel.

Press “Play” and step inside a TBM for a few minutes.

Metro Line 6 – for modern and sustainable public transport in Bucharest

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On 7 July 2026, the United Nations held the first annual meeting to review the progress made under the “UN Decade of Sustainable Transport 2026–2035” – the UN Decade of Sustainable Transport Annual Stocktake.

The event, held as part of the High-Level Political Forum on Sustainable Development, highlighted the role of sustainable transport in accelerating the implementation of the Sustainable Development Goals. The discussions covered passenger and freight transport and their links with economic development, sustainable infrastructure, jobs, sustainable energy, inclusive cities, climate action and health (details here: Official programme of the HLPF 2026 events – UN).

The UN Decade of Sustainable Transport was established by the UN General Assembly through Resolution A/RES/78/148, for the ten-year period that began on 1 January 2026. The initiative seeks to accelerate the development of safe, accessible, efficient, resilient and sustainable transport systems (further details here: UN General Assembly Resolution A/RES/78/148).

Sustainable transport means more than cutting emissions

The UN implementation plan for 2026–2035 shows that sustainable transport is not limited to protecting the environment. It must give people safe and predictable access to jobs, education, healthcare, markets and other opportunities.

Among the priority directions are the expansion of high-quality public transport, reducing dependence on cars, improving urban connectivity and developing accessible, safe, reliable and frequent services. According to the UN, investment in public transport can help reduce emissions and pollution, and can also improve access to opportunities for residents and for the business community.

Metro Line 6 – a European capital’s answer to the need for sustainable mobility

For Bucharest and its metropolitan area, these international objectives take concrete shape through the development of Metro Line 6. The new line will have 14.2 kilometres of double track and 12 stations, connecting the capital’s metro network with residential, retail and business areas in the north of Bucharest, with the town of Otopeni and with Henri Coandă International Airport.

By extending high-capacity public transport along the Bucharest–Otopeni corridor, Metro Line 6 will offer an alternative to road travel. Shifting part of these journeys from the car to the metro can help reduce the pressure on traffic, local pollution and transport-related emissions.

The impact will also be social. The stations of the new line will bring public transport closer to the communities in the north of the capital and in Otopeni, making it easier to reach jobs, services, education, retail areas and airport infrastructure.

A local contribution to the Sustainable Development Goals

Metro Line 6 is relevant to several of the goals of the 2030 Agenda:

  • SDG 9 – Industry, innovation and infrastructure, through the development of modern public transport infrastructure;
  • SDG 11 – Sustainable cities and communities, through wider access to a high-capacity public transport system;
  • SDG 13 – Climate action, by creating the conditions for shifting journeys from individual road transport to public transport;
  • SDG 8 – Decent work and economic growth, through better access to business areas, jobs and airport infrastructure.

The project’s contribution to these goals does not come from building new infrastructure alone. It will also depend on the quality of the future service, on the accessibility of the stations, on integration with other modes of transport and, above all, on the number of people who choose the metro for their journeys.

Metro Line 6 is therefore an investment in the way Bucharest and its metropolitan area will develop in the future: better connected, more predictable and more sustainable.

15 June marks International Wind Energy Day / Global Wind Day, a moment dedicated to energy produced with the help of wind and to the role it can play in the transition towards a more sustainable energy system.

Closer to the city, closer to the future: how Metro Line 6 brings people nearer to their opportunities

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For a family in Otopeni or in the north of Ilfov county, the journey into Bucharest is not just a few kilometres on a map. It means mornings spent in traffic, time lost on the road, fewer hours with the family and, at times, opportunities that are harder to reach.

This is why sustainability is not only about cleaner air, lower emissions or more efficient technical solutions. It is also about people. It is about easier access to work, to school, to services and to the places where each of us builds a future.

Seen in this light, Metro Line 6 is more than a metro line. It is a new link between communities and the city, between home and workplace, between school and family, between the present and tomorrow’s opportunities.

Commuting is not just lost time

The daily journey to work or to school has a greater impact than it might seem at first sight. A study carried out by researchers Raj Chetty and Nathaniel Hendren at Harvard University, based on data covering some 40 million people, showed that commuting time is one of the most important factors associated with the chances of social mobility. The conclusion is that when people have access to reliable, predictable and affordable transport, they are more likely to reach better jobs, education and essential services.

The same idea is supported by mobility specialists. The International Transport Forum, part of the OECD family, stresses that the role of transport is to bring education, health, jobs and everyday activities closer to people.

Good transport does not simply move people from one point to another. It gives them greater freedom of choice. It makes everyday life simpler. It opens up routes that might otherwise seem too long or too difficult to travel.

A young community, growing fast

The area around Metro Line 6 is one of the most dynamic in Romania. Between the 2011 and 2021 censuses, Ilfov county recorded one of the largest population increases in the European Union, at around 40%. At the same time, Ilfov is the youngest county in Romania, with an average age of 38.6 years.

Behind these figures are people: young families, children, parents who work in Bucharest, pupils and students who commute every day, communities that are growing and that need better links with the city.

This growth also brings challenges. More and more people travel daily between Ilfov and Bucharest, and the roads are becoming increasingly congested. For a pupil attending secondary school in the capital, for a student or for a parent who works in the city, every hour spent in traffic is an hour taken from personal time, from rest, from family life.

What Metro Line 6 changes for the community

This is where Metro Line 6 comes in. On the North Section, Lot 1.2 Tokyo – Aeroport Otopeni, the new metro line will connect the northern area of the capital and the town of Otopeni with the Bucharest metro network and with Henri Coandă International Airport.

Stations such as Bruxelles, Otopeni, Ion I.C. Brătianu and Aeroport Otopeni will bring high-capacity public transport closer to the communities that need it day after day.

For the people living near the line, this means greater predictability. A teenager will be able to reach secondary school or university more easily. A parent will be able to get to work without depending constantly on the car or on road traffic. A family with a single car, or with no car at all, will have more options.

It also means fairer access to opportunities. Because when public transport becomes closer and more efficient, people’s chances no longer depend so heavily on distance, on traffic or on owning a car.

More than transport

The benefits of a metro line do not stop at the time saved on the journey. Modern transport infrastructure can support the development of the areas around the stations, encourage new services to appear, attract investment and make communities better connected.

Over time, the areas around the stations can become livelier, more accessible and better integrated into the life of the city. Places where people do not merely pass through, but live, work, study and make plans.

A metro that brings people closer

Metro Line 6 is not only an investment in infrastructure. It is an investment in time saved, in easier access, in mobility and in better chances for the community.

Through this new link with Bucharest and with Henri Coandă International Airport, people in the northern area of the capital and in Otopeni will be closer to the places where they work, study and build their future.

Today we are building the infrastructure that will, tomorrow, bring communities closer to their opportunities. Because a sustainable city is, above all, a city in which people can reach one another more easily.

From unpredictable traffic to predictable time: what Metro Line 6 will bring

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How many times have you set off for the airport without knowing how long it would take? The distance from Gara de Nord to Henri Coandă International Airport is about 17 kilometres. The same journey takes, depending on the hour and the day: 20–25 minutes on a Sunday morning and 60–90 minutes on a Thursday at 17:00. This unpredictability is not a minor inconvenience — it is an invisible tax on your time.

The metro works differently. There are no jams and no unpredictability: the train leaves at regular intervals and covers the route in the same time — the same at 7:00 in the morning as at 18:30 in the evening. Predictability is, in itself, a resource.

The gain compared with the rush hour is easy to calculate: Metro Line 6 will cover the route from end to end in 22–25 minutes. Compared with 60–90 minutes by car — according to the TomTom Traffic Index 2025, Bucharest — a saving of 50 minutes per journey means: 50 minutes × 2 journeys a day × 250 working days a year ≈ 25,000 minutes ≈ 416 hours ≈ 17 days and 8 hours recovered every year. This is not a statistical average — it is real time, your time, which you currently spend in traffic.

And for the 16 million passengers who pass through Henri Coandă Airport every year — according to Bucharest Airports statistics — predictable access to the airport also means something else: being able to plan precisely, without the margin of error imposed by traffic. Metro Line 6 helps you save time.

Sources: TomTom Traffic Index 2025 – Bucharest | Bucharest Airports – Traffic statistics | GD 930/2016 – Technical and economic indicators, Metro Line 6

How Metro Line 6 can ease the pressure on Bucharest traffic

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According to the TomTom Traffic Index 2025 (data for 2024), Bucharest ranks 3rd in Europe and 22nd in the world for traffic congestion. The average travel speed in the city is 13.3 km/h, and a driver loses an average of 171 hours a year because of traffic — the equivalent of 7 days and 3 hours.

According to the technical and economic indicators approved by Government Decision 930/2016, Metro Line 6 will have a transport capacity of 50,000 passengers per hour, per direction. A study published in Nature Cities (2025) confirms that metro systems significantly reduce car use in European cities. Based on the experience of similar projects, between 15 and 25 out of every 100 passengers on a new metro line are former drivers who choose to leave the car at home — which, for Metro Line 6, could mean thousands of fewer vehicles every day on the capital’s northern corridor.

On saturated arteries, a reduction of 15–20% in traffic volume increases the average travel speed by 20–35% for everyone — including those who continue to use the car. (Transportation Research Board – Highway Capacity Manual, 7th Edition, 2022).

European precedents confirm the trend: after the M2 line opened in Warsaw (2015), traffic on the parallel corridors fell significantly, according to Warsaw Metro. Cities with extensive metro networks, such as Vienna or Stockholm, consistently record some of the lowest congestion indices in Europe.

Less stress in traffic is not a slogan. It is a mathematical consequence of Metro Line 6.

Sources: TomTom Traffic Index 2025 – Bucharest | GD 930/2016 – Technical and economic indicators, Metro Line 6 | Nature Cities (2025) – Prieto-Curiel et al., modal shift metro | Transportation Research Board – HCM 7th Ed. (2022) | Warsaw Metro – M2 Line

Metro Line 6 and the reduction of urban noise: the impact of a fully underground route

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Urban noise is not merely an everyday nuisance. At European level it is treated as an environmental and public health issue. Directive 2002/49/EC on the assessment and management of environmental noise establishes a common framework for identifying, preventing and reducing the harmful effects of noise exposure, particularly in large urban agglomerations and in areas affected by road, rail or air traffic.

In this context, investment in electric public transport becomes essential. Metro Line 6, which will provide the direct link between Gara de Nord and Henri Coandă International Airport – Otopeni, is one such project: underground infrastructure with a direct impact on mobility and with the potential to ease the pressure of surface traffic on the capital’s northern corridor.

European data show that the noise problem is not an abstract one. According to the European Environment Agency report Environmental noise in Europe 2025, long-term exposure to traffic noise is associated with significant effects on health and quality of life. The report estimates that it contributes each year, across Europe, to numerous health problems, including cardiovascular disease and sleep disturbance, as well as to significant economic costs. Millions of Europeans are also affected by severe sleep disturbance associated with traffic noise, and the economic impact of noise pollution from transport is estimated at over 100 billion euros a year. The World Health Organization also draws attention to this phenomenon. The WHO Environmental Noise Guidelines for the European Region, published in 2018, recommend a limit of 53 dB Lden for road traffic, stricter than the European threshold of 55 dB. The reason is simple: constant exposure to noise can affect sleep, cardiovascular health and, ultimately, quality of life.

For Bucharest and the Otopeni area, the stakes are concrete. According to the technical and economic indicators approved by Government Decision 930/2016, Metro Line 6 will have a maximum transport capacity of 50,000 passengers per hour, per direction. This capacity can absorb a significant flow of passengers who today use road transport, helping to reduce the number of cars on the DN1 and on the adjacent arteries.

The more cars there are in traffic, the higher the noise level. Conversely, every journey shifted from the car to electric public transport means less pressure on the city. Metro Line 6 works in two directions: it carries people underground, with no noise at the surface along the Gara de Nord – Aeroport Otopeni route, and it helps reduce road traffic on one of the busiest mobility corridors in the Bucharest area.

The benefits will be felt both by residents of the areas along the alignment and by those who continue to use the DN1. Smoother traffic implicitly means less noise from engines, braking, acceleration and horns.

Quiet is rarely the first argument when we talk about infrastructure. More often, we discuss speed, capacity, connectivity or safety. But in the case of Metro Line 6, acoustic comfort becomes part of the wider change the project brings to the city: mobility that is more efficient, cleaner and friendlier to people.

Sources: EEA – Environmental noise in Europe 2025 | WHO – Environmental Noise Guidelines for the European Region 2018 | Directive 2002/49/EC | GD 930/2016 – Technical and economic indicators, Metro Line 6

Metro Line 6: fewer emissions on the route between Bucharest and Otopeni Airport

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Transport is one of the sectors in which Romania must reduce the pressure on the climate and on air quality. According to Romania’s Long-Term Strategy for reducing greenhouse gas emissions (GD 1215/2023), between 1990 and 2019 emissions from the transport sector rose by 41%, reaching 18,937 kt CO₂ equivalent in 2019, with road transport as the dominant source — around 96% of the sector total.

source: https://sgg.gov.ro/1/wp-content/uploads/2023/11/ANEXA-1-21.pdf

On the DN1 – Otopeni – Bucharest corridor, this reality is visible day after day: the link between the capital, the northern area and Henri Coandă International Airport depends largely on cars, taxis and other road vehicles. Metro Line 6 changes that calculation, offering a public transport alternative that is fast, predictable and with far lower operational emissions per passenger.

Car versus metro
Here is a comparison, taking as a reference the road distance of roughly 16–17 km between the Gara de Nord area and Henri Coandă International Airport / Otopeni. Our World in Data indicates, on the basis of UK government reporting factors, around 170 g CO₂e/km¹ for a petrol car and around 35 g CO₂e per passenger-km for national rail transport.
For urban electric systems of the light rail / metro type, the 2024 UK government methodology (DESNZ – GHG Conversion Factors) indicates an average of 26.16 g CO₂e per passenger-km, and for the Glasgow Underground a value of 34.70 g CO₂e per passenger-km. These values are international benchmarks for comparison, not official factors specific to Metro Line 6 or to Romania.
Applying these benchmarks to a distance of 16–17 km, a car journey with a single occupant generates approximately 2.7–2.9 kg CO₂e one way, or 5.4–5.8 kg CO₂e for a return trip. For urban electric transport (26–35 g CO₂e per passenger-km), the same journey would generate approximately 0.42–0.60 kg CO₂e one way, or 0.83–1.19 kg CO₂e return.
The difference is significant: for every passenger who chooses the metro instead of a private car, the estimated saving is around 2.1–2.5 kg CO₂e one way, or 4.2–5.0 kg CO₂e for a return journey. Assuming a car with a single occupant, the metro can have a carbon footprint some 5 to 6.5 times smaller per passenger-km, depending on the emission factor used and on how heavily the system is loaded.

The other emissions matter too
CO₂ is not the only relevant pollutant. Road traffic generates nitrogen oxides, carbon monoxide and particulate matter, PM10 and PM2.5. According to the European Environment Agency (EEA) – Emissions of air pollutants from transport, the pollutants emitted by transport contribute to the deterioration of air quality and put pressure on human health. Although exhaust emissions have fallen in recent decades, particles from the wear of brakes, tyres and road surfaces remain an important component of the pollution generated by road transport.
The electric metro produces no exhaust emissions along its route. Therefore, for journeys transferred from car or taxi to the metro, Metro Line 6 will help reduce local emissions in the areas it crosses and ease the pressure created by road traffic on the Otopeni – Bucharest corridor. The benefit is not only climatic but also urban: more public transport means more predictable mobility, a more efficient link with the airport and a real alternative for the residents, employees and visitors of the northern area of the capital.

Metro Line 6 is a public utility project of national interest, which provides the link between the metro network and Henri Coandă International Airport and contributes to the development of the trans-European transport network TEN-T. The project is not only an investment in infrastructure, but also an urban mobility measure with direct effects on emissions, air quality and connectivity between Bucharest and the airport.

¹CO₂e/km = carbon dioxide equivalent per kilometre. CO₂e (CO₂ equivalent) is a unit of measurement that includes not only carbon dioxide (CO₂) but also the other greenhouse gases, expressed as CO₂ equivalent. Cars also emit methane (CH₄) and nitrous oxide (N₂O), not just CO₂. CO₂e adds them all into a single figure, converting them according to their global warming potential. In practice, for a car the difference from pure CO₂ is small, so when the article says “170 g CO₂e/km”, it can be read as “roughly 170 g of greenhouse gases per km, expressed as CO₂”. Per km means per kilometre travelled, with a single passenger in the car (or per passenger-km for public transport, where the emissions are divided by the number of people in the vehicle).

Sources:
Romania’s Long-Term Strategy (GD 1215/2023) | Our World in Data – Travel Carbon Footprint | UK Gov GHG Conversion Factors 2024 | CNAB – Statistical data 2024 | EEA – GHG emissions from transport | EEA – Pollutants from transport