How do add F_ELEV and T_ELEV to my network. I have tried several times to add it through creating a new network dataset. I have made the value for these fields to be short integer. For example I will have a road with a F and T value of 0 (ground level) and when I try to see if they will have a route, the network analysis gives me an error message. Only when I leave the values of the F and T as <Null> does the network analysis work.