I stopped the car and rescued her before she got run over in the dusky light. She must be someone's pet, because she was really calm about me picking her up. I stopped at the closest house; she didn't belong to them and they didn't know of anyone with chickens in the area. It was weird.
We brought her home and stuck her in with the rest of the flock. I posted a found ad on Craigslist. In the meantime, the kids' named her (you guessed it) "Roadkill".
Edit:
Kid 3 went out and took a picture of Roadkill this afternoon.