Abstract
In Japan, a variety of measures recently have been taken to reduce the death toll from traffic accidents, intending to improve vehicle safety by equipping air bag systems (ABS) and air bags in a car as standard parts and enforce the use of seat belts and child seats. While, "Mayday Service" in Japan, the Helpnet services were put into service in September 2000 with the object of increasing the survival rate in traffic accidents through prompt emergency notice and rapid rescue operation. In this paper, the authors will report on the background and features behind the development of an onboard vehicle navigation system adapted to the Helpnet services and on approaches taken to reduce data communication time.