The two main ideas i've had are to use either a special screen instead of the windscreen, or a special pair of glasses.
The first option is probably the best for implementation, however this idea could not be that feasable due to cost. The windscreen of a car is designed to break quite easily, so if it's breaking all the time and the system costs a fair amount people would not bother.
The second option solves this problem. You could use special augmented reality glasses instead, so when the driver/user sits down at the wheel he puts the glasses on, which are hooked up to the on-board computer system, and can use the car assistance system.
