The scene can be referring to a situation in which you are standing on, or could stand for, your own approach to the mental attitude with which you feel most comfortable. (assuming this was the driveway of your own home)
Any vehicle will represent a rational, logical way of thinking or a philosophy being used. As this one is grey, it suggests using a rationale about which there is some uncertainty. The bus being new, can imply a rationale or philosophy that appears to be good (since new things look in perfect condition). A bus would imply a way of thinking that does carry some weight or influence but a VW bus may not suggest the usual public opinion. If you see this as a family transportation vehicle, it might suggest a rationale pertaining to the family, a kind of rationale that does often carry some weight. (sister at the wheel might suggest family) Do they still make those?, can suggest that you might wonder about whether the rationale being used was more appropriate in the past.
There is an emotional aspect of yourself (represented by sister)that is using this rationale – perhaps suggesting a new (or old?)approach to a situation. While you may have some affinity or love for the feeling that is motivating a rationale, where it comes from could be the important thing here. Coming from California – out west – can imply that a feeling you have comes from or of grounds of reasoning that do not lead to further enlightenment (as the sun sets in the west).