Bicycle/pedestrian path on the Queensboro Bridge in New York City. The two trenches are worn entirely by bicycle tire traffic. These are not car tracks as the width slightly varies later. The city has done zero effort to clean the bridge paths after the snow and almost zero effort to clean protected street bicycle paths. The intended use for this path is for pedestrians to be on the right half (you can see the middle dividing white line if you look for it), and for bicyclists to use the left two quarters. You can notice the yellow line intended to divide the two directions of bicycle traffic, with about 2ft per direction. The actual spacing resulting from natural use is on display and apparently way different.
First thing I thought of.