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.