Vehicle trajectories information can enable many promising applications, but obtaining the information is very challenging. Road-side infrastructure can collect trajectory data from vehicles in the area through wireless communication in addition to many other functionalities. In this paper, we suggest the deployment of roadside infrastructure for vehicle trajectory collection. More specifically, we select intersections to install access points for collecting moving trajectory of all the vehicles in the area, while at the same time minimize the number of selected intersections. We prove the intersection selection problem is NP-complete and propose a greedy heuristic to approximately address it. The performance, efficiency and practical issues such as broadcast intervals of the scheme are analyzed in this paper. The simulation shows that our greedy approach solves the intersection selection problem efficiently and effectively.