Here's a twofer:
As you can see, I had the same problem, created by using legacy O27 track around a perilous corner (actually, all four corners!). My solution (after a painful real-life confirmation of my peril!) was to drill holes through the covering and foamboard into the chipboard base, and install sections of some quarter-inch dowels I had laying around, then run two levels of some thin wire wrapped around each dowel and secured to a ground-level nail at each end. So far, it's survived an out-of-control Marx 1829 smoker, so I think it could survive (and protect!) almost anything thrown at it!
When I decided to add an elevated track later, I
knew the turns would be an issue, so I was proactive: after mulling my options, I ended up hot-glueing tabs of 1/8th inch hardboard out from under the hardboard base, and using repurposed bamboo coffee stirrers (thanks, Einstein Bros. Bagels!) to secure a 'rail', also of made of hardboard, around the curves. Since I tend to run light-weight stuff on the el, there's been no definitive test yet, but several times I've managed to hook the end of the guard rail on my pants in passing (which is why I installed a warning flag, just out of sight above the top of the photo!) with no more damage done than repeatedly creating the need to reglue a few stirrer strips and supports!
The point is, as others have said, that there are are a number of free/low cost methods to make sure your rolling stock does not inadvertently do a credible simulation of a lemmings herd. But, if instead you favor Gomez's model train philosophy from "The Addams Family," well, there are other options . . .
