This image by Claes Tingvall needs to go viral.
I had many years living as a pedestrian in cities designed or managed for cars, including most big American cities in the least century, and I've never seen an image that better captured how that felt.
The bottomless void, in this metaphor, represents the essential unpredictability of the reckless or distracted motorist (there only needs to be one) combined with the destructive potential of their machine. The sidewalk is a narrow ledge on the edge of extreme danger. Crossing the street, even with a crosswalk, works when it works, but the rickety bridge perfectly captures the inherent risk; you're still relying on people to notice you even while they're texting, reading the newspaper, daydreaming, dozing off, flipping dials on the radio, trying to figure out the controls on their rental car, or doing any of other the things people do to handle the tedium of driving.
When we face this kind of danger in national parks, the government provides safety railings to keep us back from the precipice. We tolerate this level of danger only for well-warned hikers in deep wilderness, and for almost everyone who ventures into the city without a car.