China executes more prisoners than any other country in the world. In fact, it’s estimated that China executes four times as many prisoners as every country in the world combined.
Until recently, they did it through a firing squad. As a way to show that they care about human rights and having a more humane society, however, they’ve switched to the lethal injection.
However, to be more efficient, rather than build a lot of execution chamber all around the country, or transporting large amounts of death row prisoners (~8000 a year are executed), they have made it mobile.
The cars drive around from town to town executing people, and executions are filmed and played to local authorities to ensure that they are carried out legally. Another benefit that these mobile execution chambers have, according to their proponents, is that it’s a more visible sign that deters people from breaking laws.