Line 3 is one of the most important lines as it connects southwest Tehran to northeast, crosses busy parts of the capital city, and can help to alleviate traffic problems.

[3] The line starts from northeastern Tehran at Shahrak-e Qa'em going westward parallel to but 300 m north of Artesh Expressway, passing through Aghdasieh neighbourhood.

Then it turns south at the end of Artesh Expressway going to Nobonyad Square.

It then turns towards Sayyad Expressway and runs southward along it for about 5.6 kilometers (3.5 mi).

It then turns towards south, going under Valiasr Street for 7.7 kilometers (4.8 mi), until it reaches Rahahan Square, providing access to Tehran railway station.