What kind of vehicle is behind the sign?
The vehicles are cars.
    src        edge_attr  dst
0     3   to the left of    7
1     3      in front of    7
2     3      in front of   10
3     4  to the right of   14
4     5  to the right of   15
5     5  to the right of   11
6     6  to the right of    9
7     6   to the left of   14
8     7  to the right of    3
9     8           riding    5
10    8               in    5
11    9   to the left of   14
12    9               in   14
13    9   to the left of    6
14   10           behind    3
15   10               in   15
16   11   to the left of    5
17   14  to the right of    6
18   14   to the left of    4
19   14  to the right of    9
20   15   to the left of    5