Air pollution caused by NOx and PM from automobiles has been a serious problem in local commercial areas of large cities. There is also growing concern about an increase in gases which cause global warming. To improve this situation, high expectations have been placed in the use of low emission vehicles to reduce single-vehicle emissions and in the introduction of local joint-distribution systems for more efficient distribution.Here, CNG vehicles were used within a regional joint-distribution system, and were tested in actual fleet operations. Investigation was made of CNG vehicle performance in terms of practical usefulness, exhaust gas emissions and fuel economy. Six CNG vehicles were used for around three years. To investigate changes in exhaust emissions, exhaust gas emission tests were performed every 5,000 km. Fleet tests were also conducted to study how the vehicles were used during the daily operation.The result was that CNG vehicles were found to be sufficiently practical for a regional joint-distribution system. CNG vehicles also showed superior emission performance compared with the diesel vehicle. The combination of a joint-distribution system with CNG vehicles enhanced the effect of reduced exhaust emissions. However, it was found that fuel economy was inferior to diesel vehicles. Thus, for the promotion of CNG vehicles, it is important that fuel economy be improved, and that CNG refueling station networks be developed.