What vehicles are gray?
The vehicles are cars.
    src        edge_attr  dst
0     0          wearing    1
1     3   to the left of   10
2     3   to the left of    6
3     4   to the left of   15
4     5             near   14
5     6  to the right of    3
6     6          wearing    7
7     6  to the right of   12
8     7  to the right of   12
9     8  to the right of   17
10    8  to the right of   16
11    8  to the right of   14
12    8  to the right of   11
13    9   to the left of   11
14    9   to the left of   13
15    9   to the left of   17
16    9   to the left of   16
17   10  to the right of   12
18   10  to the right of    3
19   11   to the left of    8
20   11  to the right of    9
21   11  to the right of   16
22   11  to the right of   14
23   12   to the left of    7
24   12   to the left of    6
25   12          wearing    3
26   12   to the left of   10
27   13  to the right of    9
28   14   to the left of    8
29   14   to the left of   17
30   14             near    5
31   14   to the left of   11
32   15   to the left of   17
33   15   to the left of   16
34   15  to the right of    4
35   16  to the right of    9
36   16   to the left of   11
37   16   to the left of    8
38   16   to the left of   17
39   16  to the right of   15
40   17  to the right of    9
41   17               on   11
42   17   to the left of    8
43   17  to the right of   14
44   17  to the right of   16
45   17  to the right of   15