Being hit by a car in a nightmare means that you have to re-examine your life: think carefully, is your life out of control or is it too extreme in handling things? If you can make a careful plan in advance, take it easy and not be eager for quick success, then you will succeed.
Dreaming that a bus crashed into a car may imply that you lost control of something. It may mean that you have a conflict with someone, or it may be an inner conflict. It may mean that your development in a certain aspect is hindered and you can't make progress for the time being.