There is this one area of highway in my commute that always slows to around 60mph, down from 75mph. No idea why. My best guess is that the trucks have run out

There is this one area of highway in my commute that always slows to around 60mph, down from 75mph. No idea why. My best guess is that the trucks have run out of momentum at that point of the incline, though I don't notice this behavior at other incline crests. I run on cruise control the entire way so this is very noticable and annoying.