A Stretch of Highway Two Lanes Wide by Sarah Pinsker

Anyone who will stand still long enough will have heard me enthuse about this short story, which was my favourite short story I read last year. It was Nebula-nominated, and it's online until Hugo nominations are finished. Even if you aren't eligible to nominate for Hugos, you probably want to read this because it's brilliant.

http://www.sarahpinsker.com/highway1