About co-occurrence and edge weight

[MyNameIsmd5]

Thanks for your work. I have 2 questions.
(1) What is the meaning of co-occurrence between road segments?
(2) How do i calculate the edge weight in vehicle-trajectories based network? Tha paper said: "Edge weight indicates the frequency of co-occurrence and we only keep the top k frequent adjacency edges for each vertex."
So it means that for each vertex, you only preserve the top k edges, even if these edges all meet the conditions of β-hop?