Ford Crown Vic

I have a 1992 Ford Crown Victoria (4.7) with 150,000+ miles on it. This morning the battery light came on. At first it would light up at speeds below 55mph, and then go off once I past 55mph. Then it stayed on continuously. By the time I made it home from my 45 mile trip the Anti Lock break light was going on and off, my signals weren't working, and my power steering was failing. The battery was replaced last year, and the alternator recently tested fine. I am at a loss for what could be causing this. The alternator is easy enough to replace, but I am concerned about the signals, antilock break light and steering. Would these warning lights come on when an alternator is failing? Any ideas?