It never worked. But if I had planned way ahead and brought an empty space with me into the jam, I could be using that space to manipulate the jam. Once I get myself packed in with everyone else, I can do nothing. In order to have an effect, I must behave differently before the jam, not while trapped inside it, and not as I leave it. While doing all of the above, I once caught myself behaving normally and creating a huge traffic wave.
Bad habits die hard.
Traffic was heavy and I was in the left lane. I had to merge across several lanes in order to get to my exit. Nobody would let me in. I drove like this for a long while, then started driving fairly slow in order to drift backwards along the lane. I found a slot and got in, but now I had to merge right once more.