I once read a short story in an anthology about someone traveling by car, then gets stuck in a traffic jam. There is no obvious reason for the traffic jam, and there are no reports in the radio about it.
As the traffic jam continues for hours and hours, people in the cars start chatting, exchanging ideas, trading beverages and food, getting to know each other more or less. The traffic jam extends into days, and eventually groups start to build, negotiate with other groups, and scouts are sent to nearby farms, but get chased away for unknown reasons. Still nobody knows what causes this traffic jam and why it does not dissolve. Among other small stories, there is also a love story evolving.
Then, after a number of days, all of a sudden, traffic starts to move again. Everyone jumps back to their cars and the traffic jam dissolves too quickly for people to exchange any phone numbers, so friendships made during the traffic jams get lost, even the loving couple loses contact and everything that happened during those days appears to vanish in meaninglessness.
I think this story is originally in Spanish or Portuguese, but not sure. I believe I've read this in the early 1980s, and as far as I remember, it was in a scifi anthology that wasn't much older, but the story itself could of course be several years older.