Accidents in dreams may be of various kinds and the interpretation of a dream mostly depends on the specific type of accident. Overall, an accident in your dream is a forewarning of things which may go wrong or unhappy events to come up soon in your waking life. A car accident means that you need 'to slow down' and not to foolishly rush into anything. At the same time, a car accident may stand for your worries about the general state of your health, because automobiles as dream symbols usually signify the body.
Plane or ship accidents may literally represent a warning that you should not undertake any long-distance journey with this means of transport. However, it should also be noted the fact that if you do not plan to travel by ship but you still see such an accident in your dream, this means that it is a forewarning of unhappy events to take place in you love life.
If in the dream accident you see a dear person dying, this means that you must let go of the past, forget about old periods of sadness and grief in your life and move on towards new 'horizons'. The dream may be a sign that you must learn to live in the present time for the future time, not to 'drown' yourself in the past.
The accident may also represent a sudden change in your life, which may be for the worse or for the better - to find out about this, you should pay attention to all other elements in the dream and then find an adequate interpretation for them.