Driver HUD is located in the top-right corner of the screen. You can see it here on the right. This part of the HUD indicates the state that your driver and truck are in.
On the left of the Driver HUD you can see the eye icon. This icon indicates how tired the driver is at any moment. As your driver becomes tired, the eye will begin to blink and close, as a warning for your driver to take a rest.
Next to the eye is the truck health indicator. You can see a icon of a truck here which is light blue. When your truck takes damage, this icon will gradually fill red.
Alongside the truck health indicator, is your prestige rating icon.
n.b. The prestige icon will not be available if you are playing in Employee mode
The prestige icon starts off as a dark blue star with a zero on it, which indicates that your prestige rating is currently zero. As you complete tasks successfully, and buy new or upgrade your old trucks, your prestige rating will increase, and the star will change color.