> federal limits are 80,000 pounds gross vehicle weight, 20,000 pounds on a single axle, and 34,000 pounds on a tandem axle group that 80k pounds figure includes the truck and trailer. > tier 4 locomotives weigh a whopping 432,000 pounds  the same as 108 hippos weighing in at 4,000 pounds each. these 6-axle engines have 4,400 traction horsepower and can reach a maximum speed of 70 miles per hour pulling thousands of tons of freight. you literally couldn't pull one of those with a semi no matter how much you wanted to, let alone having it meet dot regulations to transport it you have no other choice but to move them by rail.
Canada