This driver jumped into the left lane as we approached a merging zone (Avondale Rd & 132th), tailgating the car in front of him and refusing to allow me to merge. As I merged behind him, I flashed my headlights to thank him for his consideration, and he slammed the brakes coming to a complete stop. He then sped off, which prompted another headlight flashing from me. Surprisingly, he again stomped on his brakes.