I'm a former postal worker (summer job in the 90's) and I drove some of those postal trucks. I drove the "half ton" and "quarter ton" trucks. Those are the small or very small delivery trucks you would typically see in residential neighborhoods.

Those things were named after their actual weight and made of aluminum. Obviously driving around in a 500 or 1000 pound vehicle when every other car weighs considerably more is anxiety producing. Plus the driver seat is inverted compared to every other US vehicle, so my visibility to the left side and rear was poor. Plus other drivers can't be expected to know or understand that my ability to see them is different from what is typical of other drivers. Plus if the vehicle was damaged in any way, I would be fired, even if it was clearly not my fault.

Fun times! And great memories. What a unique summer job to have while in college.