Semi-trucks are some of the longest, biggest, and heaviest vehicles on the roads. Semi-trucks — and here's what "semi" means on a semi-truck — are wide, averaging 8.5 feet, and can reach 70 to 80 feet ...

Semi-trucks are some of the longest, biggest, and heaviest vehicles on the roads. Semi-trucks -- and here's what "semi" means on a semi-truck-- are wide, averaging 8.5 feet, and can reach 70 to 80 ...