I still get carsick when reading on buses or cars. I no longer get sick when reading on trains. I used to be truly awful to take in a car (every single car-ride I got sick).

Even now, when i do get sick... I don't recover. I have to stop the car, wait half an hour (at least) before moving on (or eating, or anything apart from sitting on the ground feeling miserable).

I don't know if it's trainable... it has gotten better in the past 30-odd years... but not gone away totally.When i learned to drive - I learned how to avoid as much of the g-force-inducing movements as possible. I always choose train-transport over other transport.

but I am just one data-point.