Checking your diagram

After creating a diagram, check to make sure nothing unusual is being drawn.  For example, all your accidents are being drawn under the Missing Data section of the diagram, in this case your not getting the direction of travel fields being imported correctly.  Either because they aren't being converted in the .CNG file or because they just aren't being imported.  Also make sure that you're getting at least 2 symbols drawn for most of the accidents, if not then check your Object table file.