The dead angle range of a heavy duty truck driver at crossroads hss been found to be one of the factors in traffic accidents, especially when turning left in Japan.

Therefore, the Ministry of Transport of Japan requested five heavy duty truck manufacturers to manufacture experimental heavy duty trucks with an improved field of view. Each of them produced two types of modified trucks in September, 1979. One is called a visibility-improved vehicle of which field of view has been improved mainly by adopting supplementary windows, while the other is a low-floored vehicle of which the field of view has been improved mainly by lowering the height of the eye point.

This paper presents the results of experiment which comprises of (1) static visibility test, (2) dynamic visibility test, and (3) subjective evaluation teet by professional drivers, conducted on such vehicles.

As a reeult, it was proved that the experimental vehicles surpass current model vehicles in visibility.

In the case of the low-floored vehicles, however, many problems still remain to be solved. On the other hand, it seems to be possible to commercialize the visibility-improved vehicles without any drastic modification of the current design concept though they don't necessarily have a sufficient field of direct view.