What vehicle is on the railroad?
The vehicle is a train.
    src        edge_attr  dst
0     1  to the right of    9
1     2  to the right of    9
2     2           beside    3
3     4   to the left of    5
4     5  to the right of    4
5     5   to the left of   13
6     5   to the left of    8
7     5   to the left of    6
8     6  to the right of    5
9     6   to the left of    9
10    8   to the left of    9
11    8  to the right of    5
12    9               on    3
13    9  to the right of    8
14    9   to the left of    2
15    9  to the right of   11
16    9   to the left of    1
17    9   to the left of   12
18    9  to the right of    6
19    9  to the right of   13
20   11   to the left of    9
21   12  to the right of    9
22   13  to the right of    5
23   13   to the left of    9