I live in a different state, not close to you. A similar thing would happen a lot when I lived in the big city. People would hit their brakes or slow down toward the end of a ramp, while merging. A few times I had people come to a stop at the end of an on ramp.

So you would be reaching the speed of traffic, looking left for your spot to merge in to moving traffic. When you look straight ahead again, you end up slamming on your breaks because the person in font of you is slowing to a creep. Meanwhile traffic on the interstate is ripping by and now you have to try to merge.