What are the vehicles on the street?
The vehicles are cars.
   src        edge_attr  dst
0    0           behind    1
1    0   to the left of    9
2    1      in front of    0
3    3   to the left of    4
4    4  to the right of    3
5    7   to the left of    9
6    9  to the right of    7
7    9               on    3
8    9  to the right of    0