In this paper, we proposed a novel routing protocol called On-Demand Member-Centric Routing (OMR) over a VANET that consists of a platoon of vehicles driving in the highway environment. The goal of OMR is to aggregate 3G/3.5G bandwidth from some vehicles called Helpers to a vehicle called Requester, i.e., it belongs to multiple-source to single-destination transmission, to have cooperative video streaming service in the platoon of vehicles. For providing a better collaborate video streaming service in the platoon scenario, we considered two points in OMR. One is that each vehicle can get a more stable link between vehicles through a cost function, the other one is that the vehicle (destination) can find a set of paths using a proposed algorithm for calculating and selecting maximum node-disjoint paths to aggregate 3G/3.5G bandwidth from Helpers to Requester. According to the simulation results, OMR effectively improves the packet delivery ratio and throughput compared with using others. It also shows that the proposed member-centric routing protocol is more suitable for 3G/3.5G bandwidth aggregation in the platoon scenario over VANET.