I'd trust the ABS more than my own senses, especially if there is the slightest bit of slip on the roads.
Went down to Kempton Park racecourse today to collect a set of Bren Gun Carrier wheels that I got from a guy in Holland who re-tyres them, I use them on our big engine trolleys:
We had exactly what you describe pulling onto a roundabout, and then just around the corner was a dribble of diesel on the road from a truck or a bus, we had hit a patch where the leaking vehicle had stood for a few seconds.
Trust it, you won't go far wrong.
Peter