Taking my life into my hands

I always knew that driving in Chicago was taking a big gamble. I was reminded of that today when I went to change lanes at the same time as another person and we were both headed for the same lane. The craziest thing of all was that when I realized that the other person was going into the lane that I was most of the way in, I beeped my horn, and the car did nothing. No brakes, no swerve, no nothing. It just continued into the lane as if nothing had happened. Fortunately I could return safely to the lane I had been in and no one was hurt, but wow! When I realize someone is about to enter my lane, I usually try to get out of the way if I can. Apparently not this person. Erg.