Final answer:
There is no specific name for the condition described, but it can be understood as 'velocity adaptation' where perception of speed decreases after prolonged exposure to high speeds.
Step-by-step explanation:
The condition where you feel as though you are moving slower than your actual speed when on a freeway doesn't have a specific medical or scientific name. It is, however, related to the concept of velocity adaptation. When traveling at high speeds for a period of time, such as on a freeway, your body and brain adjust to the sensation of the speed. This can cause the perception that you've slowed down when, in reality, your speed is constant.
This sensation is tied to your senses adapting to the ongoing stimuli of moving at high speeds, which makes the speed seem less intense the longer you are exposed to it, hence the feeling of moving slower. This perception can pose a risk when you exit the freeway, as you might unintentionally be traveling faster in a lower speed limit area, posing a danger to yourself and others.