I think that according to what one does, one dresses differently. For example if one goes bike riding one should not go with the same skirt as when one goes walking. If one really has to go out in the car with a stright skirt, a practical idea would be to have or to make a wrapover that is left in the car ready to be used whenever necessary.
The problem with going out in a dress not compatible or long enough for a car or minivan and all other daily activities, and leaving something in the car to cover you when you get in and out, is that you will be stuck if you go into another persons vehicle where you don’t have the wrapover. Are you not going to travel because your clothing will then make you untznius?