Invisible area in the street
My observation at the corner of 13th street and 5th avenue identifies several sections.
First of all, street is basically separated road and walk ways, this is a common sense and known by everyone and which makes strong rule that people have to walk on the walk way and cars have to be on the road.
Focusing on the corner, cars make a stream line by driving down along 5th avenue, but some cars turn the corner and this makes another stream line. At this point, these seem one huge area in the street by cars (blue area of image above).
However, there is other area on the road, taxies. The task of a taxi is picking customer(s) up and going to their destinations. Because they always stop suddenly on the side of road to pick someone, other cars have to care driving. Therefore, taxies are individual or stand alone line on the road, and they make small area suddenly, and disappear in a few seconds. (bottom part of image above)