Location Registration means that a mobile station (terminal) notifies its location to a base station and MSC. It is helpful to page terminals in cellular system. The location is divided by zone including several cells. When the terminal goes through the boundary between two zones and enters a new zone, it has to register its location through system access procedure. If many terminals transmit location registration messages concurrently at the boundary in case of being transported by public transportation system like subway, many competitions occur and consequently many registrations will fail and have to retry. In this paper, we present the result measured in real subway environment and test system which varies some parameters in order to optimize the performance.