The subway operates on two rails, and the tram does. So what are the differences between tram and subway, and what is their "kinship"?

<h3>Surface vs Underground: Different Levels of Visibility</h3>

The most obvious difference is that trams are laid on the surface, constituting surface rail transit, making the entire construction process visible and thus having a solid presence. Subways, on the other hand, shuttle underground in cities, mostly built within tunnels underground, occasionally extending to the surface or elevated on bridges, with construction being fully enclosed. Trams are built in plain sight, garnering much more attention.

<h3>Different Construction Periods: 4 Years vs. 2 Years </h3>

The construction of subways involves massive work, including the significant time required for tunneling with shield machines. Trams, however, skip this enormous step.

Therefore, tram construction is relatively cheaper and faster. Generally, building a subway line takes about four years, while a tram only takes approximately two years. However, despite being faster and cheaper to build, trams have a smaller carrying capacity than subways. Therefore, not everyone who can squeeze into the subway can necessarily get onto a tram.

<h3>Integration with Municipal Systems: More vs Less</h3>

Due to their surface placement, trams are closely integrated with municipal road systems. Hence, the integrated design of trams and municipal road systems is a crucial factor affecting the efficiency of modern tram systems and road traffic systems. Handling the relationship between trams and municipal roads during the design phase can improve tram operational efficiency while minimizing the impact on road traffic.

<h3>Depth of Excavation: Deep vs Shallow</h3>

Although trams are laid on the surface, it doesn't mean no excavation is involved. Compared to subways, tram tracks are shallower, usually not exceeding 3 meters deep, while subway excavations can reach depths of 40 meters.

<h3>Occupation of Road Width: Occupying vs Not Occupying</h3>

Tram tracks are typically laid in the center of the road to ensure sufficient driving width. Trams often widen the road on both sides to "return the road to the road." In contrast, subways do not occupy road surface area after construction and typically do not widen roads.

<h3>Relocation of Utilities: Different Degrees</h3>

Since trams are laid on roads, the entire construction process involves open excavation on the road surface, inevitably encountering many municipal utilities. At the same time, subways involve less utility relocation because most of the construction is done underground, with only station construction requiring open excavation.

<h3>Power Supply: Different Power Sources</h3>

Subway lines establish dedicated 110kV substations to provide reliable, high-capacity power, minimizing external interference. Therefore, subways do not experience "power outages." On the other hand, trams use a semi-centralized power supply, lacking dedicated step-down substations along the line, and are directly powered by the city grid.