What is the truck on?
The truck is on the gravel.
    src        edge_attr  dst
0     0  to the right of    3
1     0  to the right of   10
2     0  to the right of   14
3     1  to the right of   10
4     1  to the right of   14
5     1  to the right of    3
6     2   to the left of   15
7     3   to the left of    1
8     3   to the left of   14
9     3   to the left of    0
10    3   to the left of    9
11    3   to the left of   10
12    3   to the left of   17
13    4  to the right of   18
14    6   to the left of   16
15    8   to the left of   18
16    8   to the left of   17
17    9  to the right of   10
18    9  to the right of    3
19    9  to the right of   14
20   10   to the left of    1
21   10   to the left of    0
22   10  to the right of    3
23   10   to the left of    9
24   14   to the left of    1
25   14   to the left of    0
26   14  to the right of    3
27   14   to the left of    9
28   15  to the right of    2
29   16  to the right of    6
30   16          next to   17
31   16             near   17
32   17  to the right of    8
33   17               on    8
34   17  to the right of    3
35   17             near   16
36   18   to the left of    4
37   18  to the right of    8