Green Tram Tracks

The Green Tram Tracks are tram lines where the space between and around the tracks is covered with grass. This concept combines public transport with green spaces. In Sofia, the first green rails project was implemented in 2015. It was a pilot project implemented together with the replacement of pavements in the area.

1. Identifying areas of concern and areas of possibility in terms of completing a project like this in Sofia.
2. Research on traffic intensity, engineering specifications and cost effectiveness of putting the green tram tracks in the chosen places.
3. Choosing a contractor.
4. Implementation.

- Use of a sub-roof drainage substrate layer for storm water runoff.
- Using Sempergreen Sedum-mix - a combination of different Sedum species (a perennial plant that does not require mowing)

The idea for green tram tracks in Sofia came from a civic initiative - "Green Rails in Sofia", created by citizens of Sofia. It gathered thousands of followers on the social network Facebook in just a few months. Another few months later, Sofia Municipality implemented the green tram tracks in the project for the reconstruction of the "Russian Monument" square.

- Reduction of noise and vibration pollution
Green tracks reduce noise and vibration caused by trams. A tramway produces, on average, 60-70 decibels of noise, while a green tramway reduces this noise by 10%.

- A solution against flooding
Ballast base or asphalt is still often chosen for laying between the tracks. Mainly, the latter makes the soil hard so that rainwater cannot drain away properly. When green ground cover is applied, a suitable system structure is selected. The undercover drainage substrate layer ensures that rainwater can run off more easily. Thus, the green tram/train route contributes to the reduction of flooding in the city.

- Cooling
Plants have a cooling effect. Vegetation between the rails lowers the temperature by up to 50%, reducing the risk of track buckling and the need for inspections. Green tram tracks also have a positive impact on the temperature in the surrounding area and contribute to reducing the urban heat island effect.

- Absorption of CO2 and particles
Sedums absorb CO2 and particulate matter, storing an average of 1.23 kg CO2 per square meter per year. This means that an 813 square metre Sedum railway absorbs one tonne of CO2 per year. 1 tonne of CO2 is equivalent to driving almost 10,000 km in a petrol-powered car.

- Biodiversity
Sempergreen Sedum-mix covers consist of different Sedum species and are therefore extremely diverse in colour and flowering period. The ecological value of this evergreen plant is therefore much higher than that of grass. Choose Sedum and welcome flora and fauna back to the city.

- Low maintenance
Succulent Sedum is a perennial and requires little care. Unlike grass, Sedum never needs mowing, saving on maintenance costs. Only periodic checks, watering during prolonged dry periods, and fertilizing are needed.

Briefly outline one or two key challenges and how they were addressed, e.g., “Limited funding was overcome through public-private partnerships”.

- Cities with heavy traffic and a well-developed tram network are ideal candidates for green tracks.
- Climatic conditions should allow for the sustainable growth of green cover.
- In areas of heavy rainfall, an effective drainage system should be provided and well planned to avoid flooding.