Discription of Events: On the I-15 heading south, this idiot decided to go from the 3 lane, to the 2 lane, to the 1 lane, cross double yellow to jump on the fasttrak lane. All with no blinker, nor even merging cautiously. I watched the entire thing happen right in front of me because he cut me off and I had to slam my brakes to not rear-end the jackass.