I used to have the same problem. I think it was from the speed of visual objects zooming at you too fast. I have learned to look at things farther away. If I forget and look at things as they zoom past, I overload quickly.

The other option is to look at something inside the car or at the car ahead of you. It took me quite some time before I could ride in the car without being overwhelmed. Before I figured this out, we took a ride in the country. I slept most of the next two days.

I have found that my comfortable speed is 35 mph or slower.