A filter-track that can be put in a train station. It recieves 3 signals as input, if the signal is:
True, do nothing.
False, delete contents.
Conflict, do nothing.
Shape, do nothing if shape matches, else delete contents.
Paint, do nothing if paint matches, else delete contents.
The signal inputs could either be on a space platform, or through a global transmitter/reciever signal through an UI on the Train Filter.
Alternatively, instead of deleting the contents, it might instead take out the contents, i.e. the filter might work as a smart Unloader.