I. Introduction
Over the past few years, the driving assistant system has attracted great attention, because it can provide an additional guarantee for operational safety. In the event of collision in rail transportation, the casualties and economic losses are usually very heavy [1]. Twenty-five people were injured in a single collision accident in Singapore at the end of 2017 [2]. Over forty-nine persons were killed and a great number of wounded in a train collision in Egypt in August 2017 [3]. Therefore, the rail transportation generally needs a higher degree of traffic safety than road transportation.