In an expressway, which lane is usually for overtaking slower vehicles?

In an expressway setting, the left lane is typically designated for overtaking slower vehicles. This lane allows for safer and more efficient passing of vehicles that may be traveling at lower speeds, as it provides a clear path for faster traffic. The design of many roadways supports the idea that the left lane is reserved for vehicles that are moving at a higher speed, thereby reducing the need for drivers to weave in and out of lanes to overtake when using the left lane. This practice not only promotes smoother traffic flow but also enhances safety by minimizing the risk of collisions during overtaking maneuvers.

The outer lane and center lane may be intended for other purposes, such as regular travel or merging, making them less suitable for overtaking. Thus, the left lane is the correct choice for overtaking on an expressway.