Interesting. I just found this instruction. I'm guessing you already did too. (Source)
For speed limits depending on the way direction, see maxspeed:forward=*.
So I would say, map that section of road with forward/backward speeds. Also, the signs should be independent nodes.
The position of the actual speed limit signs can be added as nodes beside the road/railway/waterwayGood commit messages always help me find the bugs I introduced.
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.
Like when everyone "went green"