"Metro" is called "metros" in most countries in the world (only a few countries' subways are called subway, underground, U-Bahn, T-Bana or others), and most subways will set signs at the entrance, or printed on carriages, route maps and tickets. So the sign of the subway is related to the "M" in "metros".

We see that subway LOGO all over the world have various designs. Most of them are based on the letter "M" and the cross section of the subway. In some cities, LOGO represents the whole subway system; In other cities, LOGO only represents a certain line or the company responsible for a certain line. So there is only one sign on the subway in some cities, such as Germany, Italy and Spain. And there are many subway signs in some cities, such as Russia. German subway signs are blue U, Italy is red M, Spain is red C, and Russian subway signs mostly use red italic M representing Moscow.

As an important means of transportation in the city, the subway carries different people to a certain corner of the city every day. As the image and symbol of urban subway, subway signs appear in every corner of the city. In fact, it represents the characteristics of the city, is the materialization of the city spirit, but also a display of the city's strength. Use the first phase of the logo design that reflects the city subway to show the different regions and cultures of the city from the side.