In Japan, fatal accidents in which persons are sometimes caught in heavy-duty trucks when the trucks turn left became a big social problem starting around 1976. (In Japan, the driver's seat is usually on the right hand side.) The analysis result of the accidents showed that it will be effective in reducing the accidents to improve the visibility to the left and to prevent persons from being caught under truck rear wheel. To remedy the situation, the introduction of regulations were considered which require the improvement of "indirect" visibility (visibility through mirrors), betterment of the pedestrian protection side guard, addition of the direction indicator lamp at the middle of the vehicle siden etc.. On the other hand, each truck manufacturer newly installed an auxiliary side window in the left door and enlarged the front windshield, thus improving visibility, especially to the left. This report describes the introduction results of auxiliary side window and enlarged front windshield. Thanks to the effects of these revisions, combined with those of regulations and others, the number of the fatal accidentsis now approximately half of that for 1976.