求翻译：常向前在出差乘坐各地客车、公交车时发现，用于表示始发站及终点站的客车用牌两站名之间，往往用一横或双向箭头表示循环行驶，行车方向不能一目了然。针对这一细节，他发明了向标车牌。2006年，这一发明已经取得国家专利。是什么意思？

Often forward a business trip to ride around the passenger boards a bus for said originating station and the terminus of the passenger car brand two station names, often with a cross or two-way arrows that cycle driving, driving directions can not glance. The details of his invention to the standard

Always ride on the road traveling around forward passenger vehicles, public transport, it was found that used to represent the station and the bus terminal in the name of the station, often with a cross or a two-way arrow indicates that the loop road, and driving directions cannot be at a glance. In

Often forward rides each place passenger train, the public transportation when the business trip discovered that, uses in expressing the initial sending stands and the terminal passenger train with the sign two station names between, often uses one horizontal or the bidirectional arrow expression ci

Chang Xiangqian found during a mission to fly around the bus, bus, used to represent the departure station and the terminus of passenger cars between the two station names, often represented by a cross or a two-headed arrow loops, lane direction cannot be readily apparent. For the details, he invent

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