Intercity-Expressways in Japan have almost reached total length of 7,000km, and approximately 4 million vehicles enjoy driving everyday. Meanwhile, traffic accidents on the expressways have been increasing every year. The number of traffic accidents caused by lane departure due to carelessness or mismaneuver got to 17,000 in 1999, and it was more than half of all accidents on the expressways. Also, because of our geographical characteristics, annual road closure caused by bad weather reached 20,000 hours in 1999, and it is approximately 60% of all road closures. Most of those weather-related road closure occurs when the road surface is snowed or iced, or when the visibility is very poor because of heavy snow or dense fog. Japan Highway Public Corporation (JH) has been trying to reduce such road closures by conducting some road operations, such as snowplowing or special patrolling under poor visibility; however, those operations impose a strong burden on operators because the visibility of foreground or road surface is really poor when they are needed. The common problem concerning traffic safety and road operation mentioned above is necessity of accurate positioning. That is, if vehicles driving on expressways can realize their accurate position in the lane and keep it, traffic accidents caused by lane departure can surely be reduced. Also, in case of during snowplowing or special patrolling under poor visibility, accurate own positioning will really make those operations safer and more efficient. The objective of this study is to develop some accurate positioning technologies and apply them to operation sites for the purpose of road operation improvement, especially, improvement on safety and efficiency on snowplowing and special patrolling under poor visibility. As a result of previous studies and experiments, accurate GPS, magnetic lane marker, and radio wave lane marker are regarded as possible technologies to realize the objective. In this paper, our study particularly focuses on accurate GPS and magnetic lane marker, and as the results of some our field experiments, it is found out that; accurate GPS is reasonable and easy to install but only effective under some limited conditions. On the other hand, magnetic lane markers are effective in any case but very difficult to install especially on expressways in operation.
Abstract