There was no lisp there unfortunately.
IIRC we wanted something we could use to demo Erlang at a conference and felt that a small business exchange with no blinking lights wouldn’t attract anyone. So we thought a model raiway run by Erlang would be good. And I ended up doing most of it (not like I’m complaining 
). Anyway I went slightly overboard and ended writing a complete ATC (Automatic Train Control) which could handle running multiple trains running around the track at the saame time in predefined paths and making sure they wouldn’t collide. It worked very well.
A colleague of mine then wrote a graphical viewer where you could see where the trains were and their paths. Another colleague then did a DSL for the defining the paths etc. Yes we went slightly overboard.
Unfortunately I don’t think we have any pictures of the demo system we made.
