A vehicular sensing network (VSN) is a type of wireless sensor network that empowers legacy resource-constrained WSNs by taking advantage of the rich network resources (e.g., the battery life, storage capability, and mobility) of vehicles. In this paper, we posit that the sensed data in VSNs is generally local in nature and propose a simple yet effective scheme, called To-and-Fro (TAF), for localized data dissemination. Unlike conventional wireless networks and sensing systems, the TAF scheme operates in an opportunistic manner and does not need a network infrastructure. More precisely, the scheme always forwards messages to passing vehicles if they are moving in the opposite direction. Using simulations of both synthetic and realistic network scenarios, we demonstrate that the proposed scheme is simple, practical, and effective for localized data dissemination in vehicular sensing networks. Moreover, the scheme is easy to deploy, as long as each vehicle in the network can access CPS information.