What does the secret service at the end of Changchun bus mean?

When you say secret service, it belongs to special vehicles or vehicles performing special tasks.

Most fire brigades use the term "Secret Service". This is a force to deal with urgent and dangerous problems, similar to special forces. The special police units below the detachment level can be called the special squadron, the special police units below the provincial armed police corps are the special police brigade, and the only unit in the armed police force that really dares to play the banner of the special team is the Armed Police Academy. Each detachment of the fire brigade has one or even several special squadrons.

The special service on the bus mentioned by the landlord refers to adding a car, which is also a special meaning in a sense, that is, it is not an ordinary bus. Can the landlord understand me?