Blocking traffic will get you run over or it'll get someone killed and it'll just make your movement look bad. I'm not denying your personal experiences but there are reasons the officials don't want you on the roads unorganised. It puts everyone at risk. I know, oppression is bad (I'm north Korean Immigrant Trust me I fucking know.) but just don't. You have a right to PEACEFUL protest, blocking traffic is not officially counted as peaceful due to the injury risks.
I’ve marched in the streets on multiple occasions. No one was injured by anyone but the cops. Based on these anecdotal facts I disagree. I believe it is peaceful and usually the only way to be heard.