you will have to take some precautions,if you donot want to take avomine
before travel but u should keep them handy:
Do not travel with stomach too full or empty.Let your meal digest at least 30 minutes before travelling.Avoid fatty heavy meal before travel.
Ginger candies , clove/lemon with black salt are also helpful in some cases.
Try to avoid reading while travelling by bus,its better if u sleep.
Try not to sit at the back- most jerks.
Stare/focus at a spot far away not nearby-same as in swings u have to look far to avoid vertigo
Wish u good health.