|Komatsu dump truck|
Here is a gravel truck that is just a little larger than average. It seems that for open pit mining, a truck that is too large has yet to be built. Historically the limiting factor on truck size has been the tires. No one could build a anything that ran on rubber tires that needed tires bigger than anyone had invented yet. Other issues include the fact that to get efficiency you need a loader that will fill the truck in 3 or 4 scoops, because trucks don't make any money waiting to be loaded. In mining cost per ton is everything, and bigger often provides economies of scale. You can buy a lot of rubber tired wheelborrows for the price of this puppy, but this thing only needs one driver.