The Japan New Car Assessment Program (JNCAP) was launched in
1995 in order to improve car safety performance. According to this
program, installation conditions of safety devices and the results
for braking performance and full- frontal crash test are published
every year. The side impact test was introduced in 1999. In 2000,
the offset frontal crash test was also introduced. From the
viewpoint of such a diversification of the crash tests, an overall
assessment method for the safety of cars which reflects road
accidents has been demanded. In this study, we have examined a new
overall assessment method capable of reflecting the traffic
accident situation in Japan using methods employed or planned by
USA-NCAP, Euro-NCAP, TUB-NCAP and others as references.
As the basic concept, JNCAP conducts three types of crash tests
including the full-frontal crash test, offset frontal crash test,
and side impact test to assess the dummy injury parameters. For the
portions of the body which cannot be represented by the dummy
injury parameters, the amount of car deformation is added to the
assessment.
The dummy injury parameters are set by referencing the standards
used in test methods and NCAPs conducted in overseas countries. In
a conventional assessment method, dummy injury parameters are
converted into a composite probability of the occurrence of
injuries. In the new assessment method, dummy injury parameters are
converted into scores using conversion functions. The conversion
functions used to convert dummy injury parameters into scores were
determined with reference to the risk curves relating to dummy
injury parameters and the assessment functions employed by USA-NCAP
and Euro-NCAP.
Scores converted from the dummy injury parameters are weighted
according to portions of the human body and modes of collision. The
weighting functions are determined taking into consideration the
traffic accident situation in Japan and anticipated economic
losses.
We have compared collision data for the same vehicle according
to both the JNCAP method and the Euro-NCAP method in order to
determine the differences in the rating methods. As a result, high
overall correlation between these methods was confirmed.
The rate of scores for individual cars was calculated according
to the Euro-NCAP method and the new assessment method. Cars scored
high in the Euro-NCAP method also got high points in the new
assessment method, although some minor differences were observed in
the ranking.