This video (bottom video) shows the time when protestors arrived at the intersection of Taleghani and Valiasr ave, heading toward Valiasr Square.
The duration of this rally was about 25 minutes and before arriving at Taleghani intersection, riot forces were not interfering but closed behind the crowd to block the accumulation of people. After arriving at the intersection of Taleghani and Valiasr ave, people continued toward Valiasr Square, as shown in this video. At this time, the anti riot forces shot teargas and followed people on motorcycles forcing the crowd to Taleghani ave.
I continued toward Chahar-rah Valiasr where people were blocked from going to Enghelab Square. The revolutionary guards on motorbikes hit pedestrians with batons. On my way to the subway station I saw a lot of military cars full of anti riot guard heading west, apparently to help their forces stationed at Enghelab square.