RESEARCH INTO RAISING THE MAXIMUM SPEED LIMIT FOR LIGHT MOTOR VEHICLES AND MOTORCYCLES ON NATIONAL EXPRESSWAYS

Until recently, the maximum speed limit for light motor vehicles and motorcycles traveling on national expressways in Japan was 80km/h, a speed lower than the 100km/h limit for large-sized, regular and most other motor vehicles. However, recent changes in the traffic environment such as improved vehicular performance and the implementation of traffic restrictions for tractor-trailers traveling on national expressways made it necessary to consider raising the speed limit while balancing the benefits of consistency with the need to ensure safety. To this end we analyzed a number of factors including driver and vehicular behavior during driving tests as well as statistical data for traffic accidents.Our research found nothing to suggest that operating light motor vehicles and motorcycles at a maximum speed limit of 100km/h would create problems in terms of vehicle performance, driver physiology and psychology or vehicular behavior. We did confirm that increased speed tends to lead to increased damage in the event of a traffic accident on a national expressway regardless of vehicle type. At the same time, we also concluded that raising the speed limit for light motor vehicles and motorcycles would likely have a positive preventative effect given that a more consistent traffic flow could be expected to reduce the incidence of passing and other such potential accident triggers. On the basis of our research, the Enforcement Orders of Road Traffic Law were revised and the maximum speed limit for light motor vehicles and motorcycles traveling on national expressways was raised to 100km/h on 1 October 2000