The Automatic Fare Collection System requires both high performance and high reliability. The IC (Integrated Circuit) Card Ticket System has been developed in order to improve the passengers' satisfaction and to reduce the maintenance costs. However, high performance on wireless communications lowers reliability due to the passengers' behaviors. The Autonomous Decentralized Architecture has been implemented as a solution. This paper introduces the "Autonomous Decentralized Data Consistency Technology" for high reliability and evaluates the effectiveness by the functional reliability. The results show the functional reliability is depends on the number of the application of this technology and that the decentralized models are, under particular conditions, competitive to the centralized one. These conditions are made use of the practical "Suica" system at East Japan Railway Company and the system is running satisfactory, without any fatal errors.