10 things you may not know about semi-trailers
You cautiously pass them on the highway, glancing to your right and seeing nothing but a driver’s side door, the hulking mass of metal dwarfing whatever passenger car you’re riding in or driving. As fellow travelers on the highway, we kind of take these cargo Goliaths for granted. Thanks to Popular Mechanics, here are 10 things you may not know about semi-trailers.
- About 5.6 million semi trailers (or tractor trailers) are registered for use in the U.S., almost three times the number of semi trucks (also called tractors). It was the trailer that gave rise to the name semi truck. Since the trailer has no front wheels and can be used only when connected to the tractor part of the truck, it’s called a semi-trailer. The terms “semi” and “semi truck” evolved from that. The combination units are also referred to as transports, semis, tractor-trailers, big rigs, and 18-wheelers.
- Typically semi-trailers run 53 feet long.
- One-third of all of the 1,900,000 semi trucks operating in the U.S. are registered in California, Florida, and Texas.
- There are 3.2 million truck drivers in the U.S.
- About 90 percent of trucking companies and owner-operators field fewer than six trucks.
- On average, semi-trailer trucks drive about 140 billion miles a year in America, with 68 percent of all goods in the U.S. delivered by semis.
- The two largest commodities shipped by weight on semi-trailer trucks are agricultural and building materials.
- Semi trucks make up just 15 percent of commercial trucks in the U.S., yet they travel 42 percent of all miles covered by commercial trucks.
- It is estimated that semis get roughly 6.5 miles to the gallon, although different trucks get fuel economy in a range from 4 to 8 mpg. Going up a steep hill, a truck’s mileage might drop to 2.9 mpg, but going down the same hill it might go more than 23 mpg.
- Maximum weight for a U.S. semi truck and full trailer is 80,000 pounds spread over 18 conventional wheels. But in Australia, “road trains” can have four trailers and weigh in excess of 300,000 pounds.
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