From cab design to road regulations, here are 15 key reasons these trucks are built for their unique environments.

Sometimes also known as cab over engines, these vehicles stand out immediately with their flat-face design, which eliminates the projected hood you see on the front of conventional semi-trucks.

one of America's most popular semi-truck brands. The giveaway is the distinctive flat front cab-over-engine design present on both Optimus' alternate mode and the real truck. Incidentally ...