Metro rail increases temperature in nearby areas, research shows
The metro rail has brought comfort to passengers traveling along the Uttara to Mirpur–Motijheel route in the capital. However, this rail line has also become a cause of rising temperatures. A study has found that along the 20-kilometer rail line from Diabari in Uttara to Motijheel, and within a 500-meter radius on both sides, temperatures have increased by 3 to 5.5 degrees Celsius. This is being termed a “localised temperature increase.”
However, researchers say that in the construction of large infrastructures like metro rail, the impact on the environment and ecosystem receives little importance. Their recommendation is that, to overcome the current situation, climbing plants should be planted along the metro rail pillars, and rooftop gardens should be developed on station roofs as well as on buildings along both sides of the line.
The study was jointly conducted by the Department of Geology and the Department of Disaster Science and Climate Resilience at the University of Dhaka, and the Department of Geography and Environment at Shahjalal University of Science and Technology. It was carried out with a special research grant from the Ministry of Science and Technology.
The study was published on 26 December, 2025, in the international environmental journal 'Environmental Challenges.' Its title is “Impact of elevated transportation infrastructure on urban thermal environment in Dhaka Megacity, Bangladesh.” The research used satellite data and images from 2015 to 2023.
The study says that over nine years, from 2015 to 2023, land surface temperatures along the 20-kilometer stretch from Diabari in Uttara to Motijheel increased by 3 to 5.5 degrees Celsius. It also found that this temperature increase spreads within a 500-meter radius on both sides of the rail line.
The official name of the metro rail route from Uttara to Motijheel is MRT Line-6. According to researcher Md Mohin Uddin, a lecturer in the Department of Geography and Environment at Shahjalal University of Science and Technology, this line is functioning as a “heat corridor.” He said that the highest temperature increases were recorded in Uttara, Mirpur, Farmgate, and Motijheel. To reduce the additional heat from infrastructures like metro rail, a budget allocation should be included within such projects.
The study found that the average land surface temperature along the corridor was 27.8 degrees Celsius in 2015, which rose to 33.3 degrees Celsius in 2023. The highest recorded temperature was 36 degrees Celsius in 2020.
Six researchers were involved in the study. They began the work in 2022 and completed it in 2024. The research was led by Farhad Hossain, assistant professor of the Department of Geology at the University of Dhaka. He told Prothom Alo, “Due to rapid urbanisation, such infrastructure (metro rail) is necessary in developing countries. Many trees are cut down while implementing such projects. But the impact on the environment and ecosystem receives little attention. For the first time, we have found evidence of how such infrastructure increases localised temperatures.” He added, “On one hand, we need such infrastructure to make urban life easier. At the same time, we must take measures to deal with its impacts.”
Information on how many trees were cut down to construct the metro rail infrastructure could not be obtained from either Dhaka Mass Transit Company Limited (DMTCL), which operates the metro rail, or the Forest Department.
Three reasons for increased temperature
The metro rail was officially inaugurated on 28 December, 2022. It is now operating regularly from Diabari in Uttara to Motijheel.
According to the study, the temperature increase is due to the removal of vegetation along the route, the heat absorption capacity of concrete structures, and the obstruction of air flow caused by elevated tracks and metro stations.
The study states that as trees were cut down due to the metro rail, sunlight is now falling directly on the roads. Trees protect the ground from sunlight by providing shade. Without trees, asphalt roads are directly heating up. On the other hand, the viaduct (the structure on which the metro rail runs) and stations are made of concrete. Concrete absorbs heat during the day and slowly releases it at night. As a result, heat is felt not only during the day but also at night around metro stations.
Additionally, the elevated stations and viaducts are obstructing the normal flow of air near the ground. Due to restricted air movement, accumulated heat inside the stations cannot escape, making these areas hotter. Moreover, the metro rail infrastructure acts as a second layer above existing roads. It not only heats up itself but also traps heat between the road below and the structure above.
Badruddoza Mia, chairman of the Department of Geology at the University of Dhaka, told Prothom Alo that the findings are expected. Naturally, cutting down trees and building concrete structures increases temperature. Noting that there is no alternative to infrastructure like metro rail in a densely populated city like Dhaka, he said, “A city should have 25 per cent green space. We have less than 10 per cent. Therefore, to reduce the temperature increase caused by infrastructures like metro rail, we must increase the amount of open space. Even the road dividers under the metro rail should be brought under green coverage.”