Why is transportation difficult in Tehran?

Transportation in Tehran is significantly challenged by heavy traffic congestion. This issue is compounded by several historical and structural factors:1

• Infrastructure Disruptions: The development of a modern underground train network was delayed for over two decades due to the impacts of revolution, war, and insufficient funding.1
• Rapid Urban Expansion: The city’s rapid growth and the expansion of transport networks have often occurred at the expense of the old city's fabric, leading to fragmentation and overcrowding.12
• Suburbanization and Density: High population density and the process of suburbanization have increased the strain on existing transit systems.34
• Environmental Constraints: The city's geography, surrounded by mountains, traps pollutants generated by motor vehicles, which further complicates the urban environment and mobility.5

While infrastructure projects, such as the expansion of highways and the introduction of underground rail lines, have been pursued to mitigate these problems, movement across the city remains a significant daily challenge for residents.12