diff --git a/aequilibrae/transit/SF_graph_builder.py b/aequilibrae/transit/SF_graph_builder.py
new file mode 100644
index 000000000..1027c1375
--- /dev/null
+++ b/aequilibrae/transit/SF_graph_builder.py
@@ -0,0 +1,2 @@
+""" Create the graph used by the public transport assignment alogirthm (Spiess & Florian).
+"""
\ No newline at end of file