A Transition Plan is a document that outlines what your child wants to achieve in the next few years and what support she or he will need to access these goals. For example, if further education is one of them, transport to college may no longer be provided and travel training will be essential in order for this to happen.
"…The Transition Plan should draw together information from a range of individuals within and beyond school in order to plan coherently for the young person’s transition into adult life. Transition Plans, are not simply about post-school arrangements. They should plan for ongoing educational provision, under the Statement of Need as overseen by the Local Educational Authority" (Special Educational Needs Codes of Practice, Para 9.51)
We have a Transition Plan Template here provided by Paradigm as an example of good practise. What you will find is that a lot of the professionals involved with your child are struggling with the time they have available. The use of a template like this can help everyone involved.