The Chinese company was selected for the line 4 contract last autumn and has now appointed China's Chang Chuto manufacture wagons for the line. The line will run 40 kilometres from Kazem Abad in northeast Tehran to Eslam Shahr in the southwest. The project is technically difficult because of the steep gradient and resulting problems with drainage. The client is the Tehran Urban & Suburban Railway Company (TUSRC).

Rtico, a subsidiary of state-owned Industrial Development & Renovation Organisation (IDRO), is expected in the coming weeks to appoint a foreign partner to work on line 3. Potential candidates include Germany's Siemens, which bid for the line 4 work, Canada's Bombardierand China's CTIC, which bid for line 3.

There are two options for the work: supplying 160 wagons for line 3 alone; or setting up a new factory in Iran to build 700 wagons over a longer period for service across the metro system. The successful company is likely to work with Rtico on the power switching and communications systems for line 3.

The line will be 20 kilometres long and run along the east-west axis of Tehran above Azadi and Enqelab streets from Shahrake Ekbatan in the west to Dowshan Tappeh in the east. Prequalification is under way for the extension of line 1 to the new Imam Khomeini International Airport to the southwest of the city. The work will require the laying of nearly 50 kilometres of track and seven new stations.