The answer is probably a reflex.
Answer: it is the second one (squeezes together)
If your car is changing speed by accelerating or decelerating, or changing directions by turning or hitting a bump, your body can sense these accelerations. You might be pressed against the back of your seat while speeding up or against the car door as you turn for example. If you are cruising at a constant speed, with no changes in speed or direction, you wouldn't be able to feel it. You would need to use your other senses. You could see the scenery going by through the windows, with closer objects moving by more quickly than objects in the distance. You could also hear sounds like the wind rushing by and the hum of the tires rolling on the highway.
