I-380 is a short connector between I-280 and US-101 just north of San Francisco International Airport. The bus ride on I-380 to I-280 and the Daly City BART station was one of my first experiences in California (at that time BART did not yet extend to the airport). In the years since then, I have been through this interchange too many times to count. Here is what it looks like from above:
As one can see, this actually a larger and more complicated interchanged that it should be. I turns out I-380 was going to extend westward over the mountain ridge and to Highway 1 in the town of Pacifica (along the ocean), but this extension was never built, and at this point probably never will be. It would have crossed the San Andreas fault on unstable ground, and the area that would have been the right of way now has several residential developments. But the extra pieces of the interchange remain. The roadway that would have been I-380 continuing underneath is often used by Caltrans to store equipment, while other parts like the unused bridges are pretty much abandoned.
User jasonbentley on flickr has taken a series of photos on unfinished I-380/I-280 interchange.
The freeway bed comes to a sudden end (all traffic is diverted to the ramps before this point). Beyond here, the right of way is crisscrossed with narrow gravel roadways.
This unused bridge goes over the connecting ramp from southbound I-280 to eastbound I-380. Most people traveling on the roadway below have no idea this bridge is not in use.
Do you have examples of unfinished or abandoned highways in your community? If so, please let us know.