Intelligent transport systems (ITS) are promising systems to give excellent solutions for many problems that we face in transport today. Not only road-to-vehicle communications but also inter-vehicle communications in ITS are expected to become popular in the future. On the other hand, an intra-vehicle communication network should be supported by multimedia information according to the explosive expansion of the Internet use and the like. An inexpensive transmission medium and transceiver becomes indispensable in such in-vehicle local area network (LAN) for multimedia information as these must handle full-motion video signals, without any electromagnetic interference. We have proposed on-board network architecture based on optical P1394b to realize effective inter-vehicle communications and enable all equipment which freely add and remove to the intra-vehicle network. And according to the proposed architecture, we have developed a 500-Mbit/s low-cost optical transceiver for the intra- and inter-vehicle communication network using a commercially available plastic clad fiber. An LD for the compact disk drive and a large area photodiode were adopted as low-cost and high-speed optical devices, and a logic direct driving type simple circuit having temperature compensation function was developed. Simple assembly technologies such as plastic molding and optical element press-fitting were also developed for mounting to reduce assembly cost. The total cost of the fabricated optical transceiver can be reduced less than 2/3, comparing with that of conventional one. We have performed transmission experiments and vibration tests using our optical transceivers that are mounted in on-board elements and connected to the on-board network, and have confirmed these stable operations. Experimental results show our proposed architecture and fabricated optical transceiver can play a key role in the intra- and inter-vehicle communication network.