My middle child stopped screaming in the car once she was in a forward facing carseat (she clawed at her eyes once and made them bleed). My youngest is now 7mths and has finally stopped screaming (she just leans forward and arches her neck so she can stare at me round the carseat the entire journey). I think it's mainly babies who like being carried alot that cry in prams and carseats. I know two children who have always been carsick but they actually vomit rather than scream. No useful advice except to say that they really do grow out of it and seem to forget that they ever felt that way. Oh, a small piece of advice: work out whether she cries less if she needs a nap or has just had a nap and fit journeys around that. I only drive places at certain times of the day.