The first question is who is asking for the statement. The form may differ depending on what it is to be used for. Statements for use in criminal proceedings have a fixed format in England, with a view to them being tendered in evidence at a trial. Statements for use in civil proceedings will not follow the same format. I suspect this is a "statement" similar to what the police now send out to witnesses because they have not got the man power to take a proper statement. You may find that if your account is relevant to any proceedings someone will come and take a more formal statement later.
statements should be expressed in the first person and only relate what you saw yourself. anything else is hearsay and should not be in the statement, unless it is something which someone told you which needs to be in to explain your own subsequent actions.
A word of warning: were you involved in the accident? If so, then depending on the circumstances you must be wary of incriminating yourself in the statement. If you think there is any chance that you may be in the firing line then don't give a statement without taking advice first.