We have been studying a technology for the transmission of additional information for data broadcasting, such as regional information, using terrestrial digital broadcasting services assisted with the Intelligent Transport System (ITS). This information is transmitted via the Dedicated Short-Range Communication (DSRC), which is a scheme for road-to-vehicle communication. This paper describes improvements to the DSRC communication procedure to make it feasible to receive more information securely during the short time in which a vehicle passes under a DSRC road-side antenna.