What is the train on?
The train is on the bridge.
    src        edge_attr  dst
0     0               on    3
1     1               by   11
2     2  to the right of    6
3     4               on   11
4     5               by   11
5     5               by    2
6     6   to the left of    8
7     6   to the left of    2
8     7               in   11
9     8               on    2
10    8  to the right of    6
11    9               by   11
12   10               of    6