Improving driving safety has been a top objective for vehicular ad hoc networks (VANETs). However, the lack of sensing in the absence of cars ahead on the road and frequent network disconnections specific to VANETs could lead to driving hazards: These networks cannot detect dangerous road conditions with good accuracy and cannot guarantee timely propagation of alert messages. To address these problems, this research proposes to merge inexpensive wireless sensor networks (WSNs) with VANETs to create a VANET-WSN symbiotic architecture. In this architecture, sensor nodes are deployed along road sides to detect dangerous road conditions and facilitate timely information sharing among vehicles; in return, VANETs provide richer computation, communication, storage, and power resources to help WSNs overcome their resource constraints. On top of this symbiosis, more effective on-road information systems for safe driving can be deployed. The main objective of this project is to explore the design and implementation of a prototype VANET-WSN symbiotic system and conduct research to test and measure the feasibility and performance of the proposed architecture. Additionally, a number of real applications built and evaluated on top of this architecture help identify and address architectural challenges in supporting application development and deployment. This research is anticipated to produce first-hand experimental results that will lead to a more accurate and comprehensive understanding of the scientific and engineering principles behind the VANET-WSN symbiotic architecture, and thus will contribute to developing new and practical technologies for significantly improved driving safety.