I guess this is a surprise for some people; but, ambulances use roads. Medical workers who need to get to the hospital use roads. Working class people who need to get to their jobs to pay rent use roads. Especially during the pandemic, people are getting their food delivered by people who, suprise suprise, use roads.
There's a way to properly protest in the middle of the road. MLK did it. The march was organized and permitted so people could plan for it and work around it. Incidentally, if you're on the other side of the Skokie case, you're advocating for a legal system that would have shut down MLK's march on Selma - not because the ideas are similar; but, because the ideas were both wildly unpopular and direct democracy would have shot them down.
Just showing up and blocking traffic spontaneously should make you a speed bump. Just the other day a woman in the UK became permanently paralyzed because she couldn't get to the hospital while she was having a stroke.
What's the utility of this form of protest? The first drivers of the first cars that you block see your signs and get pissed off at you. If you make national or international news, you're the assholes who blocked ambulances from getting people to the hospital because you think that your ideas were more important.
I don't think that it's morally or philosophically inconsistent for me as a First Amendment fundamentalist to say that, if you're protesting in the street, handle it like a marathon or a bike race so people can plan around it. If you're not gonna do that, hold your protest on the sidewalk or in a park or something.