Also check the config file for this:
attached-trigger
{
  loadtrg1
  {
    att                                 "a.track0b"
    radius                              30
    track                               "load_track"
  }
}
Increase the radius.
Or you can use the ProtoLars industry tracks, drie you consist ovet the middle of the traqck and leave it there without issuing any other commands the cars will load what they are configured for with the industry commodity. 
John