I'm afrais no free specialized software exists. You can, howerver, use a general simulation tool. An interesting overview and discussion can be found in Article Railroad capacity tools and methodologies in the U.S. and Europe
I DOWNLOADED THE STUDENT VERSION OF ANYLOGIC .. BUT WHEN I IMPORTED THE SHAPE FILE OF PAKISTAN RAILWAYS I M NOT ABLE TO SEE THE RAIL YARD AFTER ZOOMING TO 3000 PERCENT ..PLEASE GUIDE