Tank train

The Tank Train is a hybrid Fire Nation war vehicle, combining land train and armoured tank. It is primarily used as a means of transportation, designed to travel at high speeds, over most terrain, and able to haul large amounts of people or cargo across great distances.

History
This vehicle is featured exclusively in "The Chase". Azula and her cohorts use this vehicle to track Aang and his friends throughout the episode.

Aang and his friends are tired from lack of sleep, and, as Sokka replies, "I'm just gonna find the softest clump of dirt." The vehicle is apparently fast, because as soon as the kids lay down, Toph senses the machine and tells it to the group. Finally they decide to face the machine, and find out Azula, Ty Lee, and Mai are inside it, tracking them down. After Appa gets a bath, Aang uses some of Appa's fur to lead them off their trail, unfortunately for them, Appa knocks off part of the trees while he was taking off, something Azula takes note. The girls then ditch the machine, with Azula following Aang's trail, and Mai and Ty Lee following Appa. The tank-train is never seen again.

According to the creators, the Tank Train was piloted by Lo and Li.

Design
By using the concept of their tanks and building upon it, the Fire Nation was able to make a vehicle powerful enough to go virtually anywhere and large enough to transport people as well as weapons. The tank-train is the size of a regular train and consists of several cars. The first car is the work-horse, it houses the engine of the vehicle which runs on Firebending and coal power. The tank-train can often be spotted from miles away because of the plumes of smoke and steam bellowing from its engines. The first car also has a functional design; the sharp, armored plow on the front is used to batter a path through obstacles and prevent large objects from getting underneath the train and damaging the undercarriage. There are also two huge grappling hook cannons on eithe side of the car. The next two cars are for hauling things. These cars can be added and removed as needed.