The returns do not provide information about the causes of the accidents, nor do they distinguish between accidents on the southbound lanes and those on the northbound.It should be noted that this figure is based upon the data which are held in the central statistical database and which were collected by the police at the time of the accident and subsequently reported to the Executive. They may differ from any figures which the local authority would provide now, because they do not take account of any subsequent changes or corrections that the local authority may have made to the statistical information, for use at local level, about the location of each accident, based upon its knowledge of the road and area concerned.