The semi-truck or eighteen-wheeler is a monster that dominates the road and renders insignificant all the passenger cars that surround it. These oversized vehicles are formed by a combination of a tractor unit attached to a semi-trailer and their sheer size makes them impossible to ignore.
Every day, hundreds of thousands of semi-trailer trucks make their way down this country’s highways. And while these monsters may be intimidating, they are the key to delivering products and transporting materials across the U.S.
Perhaps some drivers think of Steven Spielberg's first full-length movie, Duel, when they encounter a big eighteen-wheeler on the highway. For many, Duel was a mediocre made-for-TV movie with a rather weak plot. It was nothing more than 74 minutes of a tired old semi-truck hounding David Mann (played by Dennis Weaver) in his orange Plymouth Valiant. However, it made the sixth spot on The Drive's list of the top ten car movies of all time and Spielberg succeeded in making some viewers believe it could happen to them.
Semi-trucks have a long history, with the first one built in the nineteenth century, and they have become the principal method of transporting goods across the country. They are the life force of our existence: the source of food products on supermarket shelves, the gas that fuels our cars, and of course, Amazon deliveries. For that reason, it is worth knowing a bit more about them. Here are 25 facts about big-rig trucks most people didn’t know or couldn't believe.
25 Luxury for The Long Haul
Truck owner-operators are much more common in the U.S. than in Europe. These drivers own their trucks and spend most of their time on the road, living in their vehicles for months at a time.
For the convenience of the driver and other passengers, many of these semis have a sleeping area built into the design. Semi-trucks with conventional cabs instead of cab-over configurations feature a longer wheelbase, which creates a lot of room inside. The space behind the driver’s cabin can be customized to meet the driver’s requirements. Luxury varies from truck to truck. Even basic sleeper cabs incorporate beds, closets, tables, refrigerators, sound systems, and flat-screen TVs.
24 Semi Engines Can Run Continuously
Semi-truck diesel engines are designed to run for extended periods. The only mandatory shutdown of a big rig is for periodic maintenance. However, the practice by truck drivers of leaving a semi engine idling can result in an enormous cost in wasted fuel, as well as senseless environmental damage.
According to the American Trucking Association, the hundreds of thousands of diesel trucks idling at truck stops across the U.S. are causing a significant emissions problem. With over 1.3 million long-haul diesel trucks on U.S. highways, billions of hours are spent idling. Some jurisdictions have passed anti-idle laws, making it illegal to keep a semi-truck engine running when not moving down the road.
23 Why It is Called a Semi
Why is something so massive called a “Semi?” A semi-trailer truck is the combination of a tractor unit and one or more semi-trailers to carry freight. The trailers are called semi-trailers since they are devoid of front wheels and need the support of the semi-tractor to make a move. A trailer can only roll when it is connected to the tractor. A fifth-wheel coupling or hitch attaches the semi-trailer to the tractor and much of the trailer’s weight is borne by the tractor.
The trailer portion of a semi-truck is also equipped with a powerful braking system. The braking system remains in a locked position unless attached to the front tractor unit. Once connected to a tractor, the lock releases automatically, allowing the trailer to roll.
22 Nearly One-third of All Semi-trucks Operate in Three States
Driving behind a big semi-truck can be frustrating, at times. Not only is the view ahead blocked by a tall, wide trailer, but the pace slows to a crawl when a semi must go up even the slightest grade. Perhaps the biggest nightmare is being stuck behind a slow-moving truck on a two-lane mountain road, where passing is out of the question.
The best way to avoid truck traffic is to live and drive in a state with fewer trucks. But few people select their place of residence based on the number of trucks in the state. However, the three states with the most operating semis are California, Florida, and Texas. With more than 141 million trucks on the road in the US, California has over 15 million, Texas nearly 13 million, and Florida hosts almost 8 million.
21 Semi-Trucks Drive 140 Billion Miles a Year
According to the Federal Highway Administration, 42% of all miles driven by commercial vehicles are driven by semi-trucks, totaling 140 billion miles per year. Individual truck drivers do an estimated 45,000 miles every year, while long-distance trucks travel nearly 100,000 miles a year.
To put that in perspective, the distance from Los Angeles to San Francisco via I-5 is just over 380 miles and takes over 6 hours by car when traveling at the speed limit (or 760 miles for the round trip). A semi-truck would have to make about 60 round trips per year to equal the yearly average of 45,000 miles.
20 Semi-Trucks Were Invented in 1898
In 1896, Alexander Winton, owner of the Winton Bicycle Company and designer of engines for the new horseless carriages, began building and selling cars. His new company, the Winton Motor Carriage Company of Cleveland, produced twenty-two cars the first year and sold them to customers living across the country.
However, the only method Winton had for delivering his cars was driving each machine to its new owner. The delivery method resulted in wear and tear on the cars even before the owner could drive the new car. Out of necessity, Winton created the “automobile hauler,” the first semi-truck to deliver his automobiles, and shortly after that, he began selling them to other car manufacturers in Cleveland.
19 80,000 Pound Limit?
Although 80,000 pounds is generally considered the maximum allowable semi-truck loaded weight in the U.S., many trucks legally operate at much higher weights on a regular basis. A semi-truck carrying an indivisible load, one that requires more than 8 hours of labor to disassemble, like housing units or heavy equipment, can exceed the 80,000-pound mark.
Most jurisdictions will permit extremely large indivisible loads, some weighing more than 250,000 pounds. Semis carrying divisible loads, those that can be separated into smaller loads in less than 8 hours of work, usually require a permit to go over the 80,000 lbs. Maximum weight limits vary by state, with South Dakota allowing the heaviest trucks. On non-interstate roads, it has no gross weight limit nor a limit on the number of truck axles.
18 18-Wheelers in the Movies
Films featuring semi-trucks were popular in the 1970s, including White Line Fever, Duel, Smokey and the Bandit, and Convoy. Sam Peckinpah's film, Convoy, was the most popular, grossing nearly $15 million when it was released in 1978. The film starred Kris Kristofferson, Ali MacGraw, and Ernest Borgnine.
The movie was based on the 1975 novelty song, "Convoy", that became a number-one song in the U.S. on both the country and pop charts. The song’s lyrics are comprehensible only to truckers: "… Kenworth pullin' logs, a cab-over Pete with a reefer on, and a Jimmy haulin' hogs. We's headin' for bear on I-one-O 'bout a mile outta Shakeytown, I says 'Pigpen, this here's Rubber Duck, and I'm about to put the hammer down.'"
17 Not All Semi-Trucks Have the Same Number of Gears
The average semi-truck has ten gears, making it possible to find the right transmission setting for most loads and road conditions. However, some semis-truck transmissions have three, five or eight additional gears. More gearing options make it easier for the driver to find the optimal settings for even the most unexpected or extreme driving situations.
Although much less common, automatic transmissions are also used in semi-trucks. AMT, or “auto-shift” boxes, come in two-pedal and three-pedal versions and are found in the fleets of most U.S. carriers. The automatics are more fuel efficient than manual transmissions because they never miss or skip shifts. For new truck drivers, using an automatic transmission is easier to learn than manual shifting.
16 Part of that 80,000 Pounds is Liquid
The fuel tank of a semi-truck typically holds between 100 to 400 gallons of fuel, but are sized according to the buyer’s needs. As an example, a previously owned 2011 Kenworth T660 truck can be purchased with dual 120-gallon fuel tanks, for a total of 240 gallons.
Larger fuel tanks are ideal for cross-country trips or trucks that carry heavy loads. In some cases, truck manufacturers will install larger fuel tanks on one side rather than the other to achieve an overall weight balance. Meanwhile, fuel tankers that take the gas to a gas station hold nearly 9,000 gallons! Diesel fuel is lighter than water but weighs 6.943 pounds per gallon. Therefore, a fully loaded tanker carrying diesel fuel weighs over 62,000 pounds.
15 How Semis Become More Fuel Efficient
Nowadays, cars and light trucks that operate in the U.S. are more efficient than ever before. They currently average about 24 miles per gallon. Semi-trucks, on the other hand, are much less fuel efficient, averaging about 5.6 miles per gallon of diesel. Furthermore, semi-truck mileage varies greatly depending upon load and driving conditions. A truck climbing a steep hill might get as low as 2.9 mpg while going down the same hill the mileage may increase to more than 23 mpg.
Truck manufacturers are now using aerodynamic enhancements to improve semi-truck fuel efficiency. Fairings that smooth out the leading edge of the trailer, side skirts that discourage air turbulence under the trailer, and rounded caps covering the rear trailer doors combine to improve fuel mileage.
14 Most Popular Semis
There are more than 150 truck manufacturers in the U.S. alone and many more in other countries. In 1915, 33.8 million registered trucks were in use for business purposes, not including trucks used by government and on farms. Of all trucks traveling the highways, 3.63 million Class 8 trucks, including tractors and straight trucks, were in operation. Class 8 is the heaviest weight limit category, except for trucks with special duty characteristics.
Freightliner is the highest-selling brand of Class 8 semi-trucks, accounting for nearly one-third of all new semis sold each year. In 2017, the company had over 37% of the market share. Peterbilt, with 15.9% of the market, placed second, followed by International at 10.9% and Volvo at 10.5%.
13 Why Diesel?
While most passenger vehicles run on gasoline, most semi-trucks operate on diesel fuel because they have much higher energy requirements. A gallon of diesel contains more energy than a gallon of gas. The difference in usable energy can result in as much as a 30% increase in travel distance. Since semi-trucks frequently carry freight for long distances, the significant enhancement in fuel efficiency can lead to lower operating costs.
The purchase of a diesel engine is often more cost-effective because they also have a longer life expectancy than gasoline-powered engines. For the number of operating miles and the price of a semi-truck engine, the longer-lasting diesel is usually a better investment.
12 Eighteen-Wheelers are Expensive
Semi-trucks vary widely in price. A brand-new semi can range anywhere from $120,000 to $200,000. The tractor unit alone can cost up to $200,000, and the trailers can run an additional $30,000 to $80,000. The price is determined by several factors: the truck’s size, the cab configuration (for day use or sleeping), horsepower, fuel efficiency, cargo capacity, and custom features.
Semi-trucks are most often purchased using financing or leasing. However, the initial purchase or lease price is only the beginning of cost incurred while operating a semi. Additional costs include fuel, routine maintenance, regular oil changes, and insurance. The most cost-effective purchase is one that selects a model designed for the goods or materials to be transported while maximizing fuel efficiency and keeping operating costs down.
11 70% of All Goods in the U.S. are Delivered by Semi-Truck
Freight is usually transported by one of three types of shipping modes. Air: Cargo is transported by air in specialized cargo aircraft. Although it is typically the fastest mode for long-distance freight transport, it is also the most expensive. Freight transport by ship: The world’s economy depends upon Merchant shipping which carries 90% of international trade with over 100,000 commercial vessels worldwide.
Ground shipping: can be by train or by truck. Ground transport is typically less expensive than air but costlier than sea transport, especially in developing countries with inefficient infrastructures. Nearly 70% of all goods in the U.S. use ground shipping and are delivered by semi-truck.
10 Agricultural and Building Materials Lead the Pack
Contrary to what many people believe, products shipped by Amazon do not lead the list of most goods (by weight) shipped via semi-trucks in the U.S. Amazon ships an average of 1,600,000 packages a day or 608 million packages each year. According to analyst estimates, Amazon is one of UPS’s biggest customers, accounting for 5 to 10 percent of their total revenue, while FedEx claims the e-commerce giant makes up less than 3 percent of its sales.
Many of the Amazon packages are carried to their destinations by small delivery trucks without the use of semi-truck transport. By sheer weight, agricultural and building materials are the two leading goods transported by semis.
9 Antilock Brakes are Required on Semi-Trucks
An anti-lock braking system (ABS), which is used on several types of vehicles, is designed to prevent the wheels from locking up during braking and helps maintain traction with the road surface. Since September 1, 2000, Federal law has required that all new cars in the U.S. use ABS. Although heavy trucks use a different braking system than automobiles, ABS is also required by law.
Semi-trucks typically use air brakes rather than hydraulic brakes due to their reliability. The supply of air is unlimited, so when a leak occurs, the brake system can never run out of its operating fluid, as it does with a hydraulic braking system. Federal law required tractors to be equipped with ABS after March 1, 1997, and air-braked semi-trailers and single-unit trucks after March 1, 1998.
8 U-Turns Are A Challenge (and Against the Law)
The U-Turn, performed by any vehicle, car or truck, is still one of the most dangerous driving maneuvers on the road. Paramedics are called daily to treat severe trauma from accidents caused by a driver’s hasty decision to make a U-turn in traffic. In the case of an automobile, the unexpected maneuver usually does not allow time for nearby, faster-moving vehicles to change course and avoid an accident.
In the case of semi-truck, the U-turn is much slower due to the sheer size of the vehicle. The combined length of a typical semi truck’s tractor and trailer measures around 70 feet. Most highway lanes are about 12 feet wide. However, the U-turn is even more dangerous because the semi-truck frequently blocks the entire highway.
7 Self-Driving Trucks
Once merely a futuristic concept, self-driving cars and semi-trucks are now a reality. Embark, a developer of self-driving trucks, has teamed with Electrolux and Ryder to demonstrate automated, driverless transport of Frigidaire refrigerators from El Paso, Texas, to a distribution center in Palm Springs, California. A human driver currently rides in the cab for the 650-mile trip along the I-10 freeway to monitor the computer chauffeur.
However, the goal of the pilot program is to let the trucks make the trip solo. Embark CEO Alex Rodrigues says, “This is the first time someone has demonstrated this end-to-end. It showcases the way that we see self-driving playing into the logistics industry.”
6 Semi Engines Are Designed for Easy Rebuilding
While most experts agree that a properly maintained gasoline-powered truck can run for 200,000 miles, there is some disagreement regarding the lifespan of a diesel truck. Some estimate that a diesel can run at least 300,000 miles while others claim the lifespan can reach as much as 500,000 miles. In any case, a diesel will usually outlast its gasoline counterpart.
Maintenance costs over the lifetime of diesel engines are usually cheaper than those of gasoline engines because they have fewer problems. When they fail, diesel engine parts are more expensive than gasoline engine parts but semi-truck engines are designed to make the rebuilding process as simple as possible. Swapping out parts subject to wear-and-tear, including pistons, connecting rods, and bearings, is relatively easy.
5 Semi-Truck Mud Flaps Have Multiple Purposes
While mud flaps installed behind the wheels of a semi-truck help prevent dirt, mud, and other types of road debris from creating a safety road hazard for vehicles traveling behind the truck, they can also reduce drag. Wind resistance can reduce a semi-truck’s fuel efficiency by as much as one-third. However, several methods can be used to make a truck more aerodynamic, including the installation of vortex generators, fairings, drive fenders, wheel covers, and vented mud flaps.
Traditional mud flaps cause added drag under normal driving conditions and during inclement weather, they have even more impact on fuel efficiency. As an alternative, vented flaps are designed to improve airflow, reduce water spray, and make the vehicle more aerodynamic.
4 How Much Power Does It Take to Move a Loaded Semi?
The average car produces around 200 horsepower, which is enough power to carry the driver, several passengers, and luggage through city streets or on mountain roads at safe speeds. The average diesel semi-truck produces almost three times as much horsepower. Perhaps a more significant difference is the torque produced by each type of vehicle. While the average passenger car produces 100 to 200 foot-pounds of torque, the average diesel generates from 1,000 to 2,000 foot-pounds of torque.
Some specialty tractors can carry heavy weight at exceptional speeds. For example, the U.S. Army’s M1070A1 heavy equipment tank transporter is equipped with an engine that develops 700 horsepower and 1,900 ft-lbs. of torque. All that power allows it to carry a tank and crew at speeds up to 80 kph.
3 Who Drives Semis?
In the U.S. there are more than 3.2 million long-haul truck drivers that hold Class A driver’s licenses. The Class A level permits drivers to pilot vehicles with a gross vehicle weight rating of more than 26,000 pounds.
AAA's definition states, “Class A: a combination of 2 or more vehicles, including a trailer(s) in excess of 10,000 lbs., articulated buses with a Gross Vehicle Weight Rating (GVWR) exceeding 26,000 lbs., and all vehicles authorized to be driven under Class B and C, or with a regular driver's license, Class D.”
Tractor-trailer drivers can earn a good living. According to the Bureau of Labor Statistics, in 2014, drivers of heavy vehicles and tractor-trailers earned median annual wages of $39,520. These wages are above the 2014 national average of $35,540.
2 Fully Electric Semis
Several companies have announced plans to produce all-electric semi-trucks, including Volvo Trucks, Daimler (with their electric eCascadia), and of course, Tesla. The Tesla Semi, due to begin production in 2019, has some unusual features. The driver’s seat is positioned directly in the center of the cab. A jump seat behind the driver provides room for passengers.
The utilitarian vehicle has a sparse dash like the Model 3 and boasts exceptional performance characteristics. The semi can accelerate from 0 to 60 mph in less than 20 seconds while towing an 80,000-pound load. Meanwhile, Volvo plans to bring their semi to California this year as part of a demonstration project.
1 Safety First, Last, Always
Today’s semi-trucks are safer in many ways than the passenger vehicles that surround them on the highways. They must be safer because trucks are required to operate 24/7, in all types of weather. Companies want to preserve not only their drivers but also the enormous investment in their tractors and trailers.
Collision-avoidance systems, roll stability control, cameras, lane departure warning systems, and other features that are prohibitively expensive options for passenger cars are mostly standard equipment on modern semi-trucks. These advanced safety features allow a fully loaded semi to perform safely under any conditions. A loaded semi traveling at a speed of 55 mph needs nearly two football fields of road distance to come to a complete stop. That is 40 percent more than a car needs to stop.
Sources: NY Times, Truck Science, Big Truck Guide, Nodum, Quora, and Truckers News.