Vehicle

Mechanical vehicles, especially those running on petrol, are generally non existent in the Fallout universe. The most common means of transport are brahmin carts.

The war was fought mainly for resources. The last resources remaining were probably depleted in the war itself. Without resources, vehicles couldn't be driven anymore. Furthermore, it is generally accepted that after the war, much of the human knowledge was lost. The knowledge of how to tend to the high tech fusion cars that existed before the war was lost, and with it the necessary skills to repair the cars.

There were no vehicles at all in Fallout 1.

Fallout 2 featured a fully working car, the Highwayman, and high tech flying machines, known as Vertibirds.

Fallout Tactics Featured many vehicles the player could operate, and caused yet other point of controversy that ruled Fallout Tactics as non canon.