Ramp to Somewhere

Your Boulevardier noticed this recent addition to the onramp to eastbound I-580.



A couple of things strike one as odd about this. First, what's it for? Your Boulevardier's best guess is that it's for Highway Patrol or other emergency vehicles to sit in before they enter the freeway.

Second: the drainage from it. Note, if you can in the photo, the contours of the ramp and the wall behind it. The wall drains into the grate (currently surrounded by sandbags) while the pullout itself drains onto the sidewalk, or maybe into the adjacent gutter.

Thirdly: the tiny fence atop the small retaining wall. What is its purpose? A person can walk twenty feet to get around it, so it can't be to keep someone from what's on the other side. If it's to keep people from above from falling onto the ramp, another question arises: what are they doing up there in the first place?

None of this is earth-shattering news, or even the least bit important. It's just curious. If any readers know about civil engineering, an explanation would be most welcome.