Brighton Park Jct.

I have a question. Why is this busy crossing STILL such an anachronism and NOT a modern interlocked plant?

Because railroading is first and foremost a business, I suspect the answer is money. My guess is the Pennsy [which controlled the junction] had no motivation to upgrade the signaling and control system at Brighton Park because it's Panhandle line was a secondary line and the major beneficiaries would be Pennsy competitors B&O and NYC. PennCentral certainly had no money for an upgrade. Are my guesses and suspicions correct?

But why didn't Conrail and now NS upgrade Brighton Park into an interlocked plant?

I'm an engineer on the NS and regularly go through the Brighton Park crossing. This is total speculation on my part, but my guess is that the old Chicago Junction tracks we use are industrial tracks, therefore controlled by a yardmaster, not a dispatcher. We have a switchtender that operates the junction. Our whole part of that railroad is non signaled restricted speed track. I think your suspicion of money being the driving force is probably right. There really aren't that many switches to throw it's basically just diamonds. And it's worked for a lot of years, it might be the old "If it ain't broke, don't fix it" syndrom too