Why Do Pigeons Do This?

Rock Pigeons are well known city dwellers but why do they so often hang out above busy intersections? The example above, taken over Interstate Highway 5 near the JBLM Madigan Gate entrance, is just a small example. There are often many more of these birds at this overpass and I have seen this pigeon behavior numerous times at other similar locations. It confuses me. There is no food down below or shelter above, and these are certainly not quiet peaceful places to hang out. Could it be that the birds just consider this kind of location safe from predators? If anyone has an answer please let me know.

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