Bunch of architecture students who haven't figured out how the real world works. They certainly haven't figured how a railroad works. There will be a flangeway on urban girder rail trackage only. To be able to use it on most railways, you need wheels on each rail, with flanges to keep it on the 2 rails. Such "speeders" have already been invented, including bicycle-based ones (approx 70 years ago).

The vehicle shown only works on girder rail, and is very inefficient because of the balloon tire riding in the flangeway, instead of steel rolling on steel, the basis of the railroad's efficiency.

...and such abandoned tracks are...where?

I guess the Willamette Shores Trolley Line is as close as one can get. None out east (it's now the Springwater Trail Corridor). None out west (it's called MAX.) None down south (there's a few blocks of such in Salem, but in very undesirable neighborhoods, and they extend about one-two blocks. The rest of the track has been abandoned.)

so the chair is a speeder?
Doug K says :Bunch of architecture students who haven't figured out how the real world works.

A large part of the point of architecture school is to think OUTSIDE the constraints of the real world. We get PLENTY of time after we graduate to figure out how the real world works. School is a place where one can explore these ideas that simply won't fly in the real world.

I didn't get a chance to read the whole article, but from what I could glean from the images, it looks like a fascinating project!