Blog

  • Truck

    truck or lorry is a motor vehicle designed to transport freight, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame construction, with a cabin that is independent of the payload portion of the vehicle. Smaller varieties may be mechanically similar to some automobiles. Commercial trucks can be very large and powerful and may be configured to be mounted with specialized equipment, such as in the case of refuse trucksfire trucksconcrete mixers, and suction excavators. In American English, a commercial vehicle without a trailer or other articulation is formally a “straight truck” while one designed specifically to pull a trailer is not a truck but a “tractor“.[1]

    The majority of trucks currently in use are powered by diesel engines, although small- to medium-size trucks with gasoline engines exist in North AmericaElectrically powered trucks are more popular in China and Europe than elsewhere.[2] In the European Union, vehicles with a gross combination mass of up to 3.5 t (3.4 long tons; 3.9 short tons) are defined as light commercial vehicles, and those over as large goods vehicles.

    History

    Steam wagons

    Sentinel steam wagon

    Main article: Steam wagon

    Trucks and cars have a common ancestor: the steam-powered fardier Nicolas-Joseph Cugnot built in 1769.[citation needed] However, steam wagons were not common until the mid-19th century. The roads of the time, built for horse and carriages, limited these vehicles to very short hauls, usually from a factory to the nearest railway station. The first semi-trailer appeared in 1881,[citation needed] towed by a steam tractor manufactured by De Dion-Bouton. Steam-powered wagons were sold in France and the United States until the eve of World War I, and 1935 in the United Kingdom, when a change in road tax rules made them uneconomic against the new diesel lorries.

    Internal combustion

    Daimler Motor-Lastwagen from 1898
    1903 Eldridge truck on display at the Iowa 80 Trucking Museum, Walcott, Iowa.

    In 1895, Karl Benz designed and built the first internal combustion truck. Later that year some of Benz’s trucks were modified to become busses by Netphener. A year later, in 1896, another internal combustion engine truck was built by Gottlieb Daimler, the Daimler Motor Lastwagen.[3] Other companies, such as PeugeotRenault and Büssing, also built their own versions. The first truck in the United States was built by Autocar in 1899 and was available with 5 or 8 horsepower (4 or 6 kW) engines.[4] Another early American truck was built by George Eldridge of Des Moines, Iowa, in 1903. It was powered by an engine with two opposed cylinders, and had a chain drive[5] A 1903 Eldridge truck is displayed at the Iowa 80 Trucking Museum, Walcott, Iowa. Trucks of the era mostly used two-cylinder engines and had a carrying capacity of 1.5 to 2 t (3,300 to 4,400 lb). After World War I, several advances were made: electric starters, and 4, 6, and 8 cylinder engines.

    Diesel engines

    Foden diesel truck from 1931

    Although it had been invented in 1897, the diesel engine did not appear in production trucks until Benz introduced it in 1923.[6] The diesel engine was not common in trucks in Europe until the 1930s. In the United States, Autocar introduced diesel engines for heavy applications in the mid-1930s. Demand was high enough that Autocar launched the “DC” model (diesel conventional) in 1939. However, it took much longer for diesel engines to be broadly accepted in the US: gasoline engines were still in use on heavy trucks in the 1970s.[7][8]

    Electric motors

    Main article: Electric truck

    1911 Walker Electric truck on display at the Iowa 80 Trucking Museum, Walcott, Iowa.
    President Joe Biden test driving the Ford F-150 Lightning all-electric pick up at Ford’s Rouge Electric Vehicle Center

    Electrically powered trucks predate internal combustion ones and have been continuously available since the mid-19th-century. In the 1920s Autocar Trucks was the first of the major truck manufacturers to offer a range of electric trucks for sale.[9] Electric trucks were successful for urban delivery roles and as specialized work vehicles like forklifts and pushback tugs. The higher energy density of liquid fuels soon led to the decline of electric-powered trucks in favor of, first, gasoline, and then diesel and CNG-fueled engines until battery technology advanced in the 2000s when new chemistries and higher-volume production broadened the range of applicability of electric propulsion to trucks in many more roles. Today, manufacturers are electrifying all trucks ahead of national regulatory requirements, with long-range over-the-road trucks being the most challenging.[10][11]

    Etymology

    Mannesmann Mulag truck at the Finlayson factory in TampereFinland in 1921

    Truck is used in American English; the British English equivalent is lorry.

    The first known usage of “truck” was in 1611 when it referred to the small strong wheels on ships’ cannon carriages, and comes from “Trokhos” (Greek) = “wheel”. In its extended usage, it came to refer to carts for carrying heavy loads, a meaning known since 1771. Its expanded application to “motor-powered load carrier” has been in usage since 1930, shortened from “motor truck”, which dates back to 1901.[12][13]

    “Lorry” has a more uncertain origin, but probably has its roots in the rail transport industry, where the word is known to have been used in 1838 to refer to a type of truck (a goods wagon as in British usage, not a bogie as in the American), specifically a large flat wagon. It might derive from the verb lurry (to carry or drag along, or to lug) which was in use as early as 1664, but that association is not definitive.[14] The expanded meaning of lorry, “self-propelled vehicle for carrying goods”, has been in usage since 1911.[15][16]

    International variance

    Further information: List of truck types

    Trucks parked near Plaza, by the side of Highway in USA
    In Pakistan and India the majority of trucks are colorful and decorated.

    In the United States, Canada, and the Philippines, “truck” is usually reserved for commercial vehicles larger than regular passenger cars, but includes large SUVs, pickups, and other vehicles with an open load bed.

    In Australia, New Zealand and South Africa, the word “truck” is mostly reserved for larger vehicles. In Australia and New Zealand, a pickup truck is frequently called a ute (short for “utility” vehicle),[17] while in South Africa it is called a bakkie (Afrikaans: “small open container”).

    In the United Kingdom, India, Malaysia, Singapore, Ireland, and Hong Kong lorry is used instead of truck, but only for the medium and heavy types, while truck is used almost exclusively to refer to pickups.

    Types by size

    See also: Truck classification and List of truck types

    Ultra light

    Often produced as variations of golf cars, with internal combustion or battery electric drive, these are used typically for off-highway use on estates, golf courses, and parks. While not suitable for highway use some variations may be licensed as slow speed vehicles for operation on streets, generally as a body variation of a neighborhood electric vehicle. A few manufactures produce specialized chassis for this type of vehicle, while Zap Motors markets a version of their Xebra electric tricycle (licensable in the U.S. as a motorcycle).

    Might-E Truck from Canadian Electric VehiclesMitsubishi Minicab MiEV battery-electric truckDairy Crest electric milk float truck

    Very light

    Popular in Europe and Asia, many mini-trucks are factory redesigns of light automobiles, usually with monocoque bodies. Specialized designs with substantial frames such as the Italian Piaggio shown here are based upon Japanese designs (in this case by Daihatsu) and are popular for use in “old town” sections of European cities that often have very narrow alleyways.

    Regardless of name, these small trucks serve a wide range of uses. In Japan, they are regulated under the Kei car laws, which allow vehicle owners a break in taxes for buying a smaller and less-powerful vehicle (currently, the engine is limited to 660 cc displacement). These vehicles are used as on-road utility vehicles in Japan. These Japanese-made mini-trucks that were manufactured for on-road use are competing with off-road ATVs in the United States, and import regulations require that these mini-trucks have a 25 mph (40 km/h) speed governor as they are classified as low-speed vehicles.[18] These vehicles have found uses in construction, large campuses (government, university, and industrial), agriculture, cattle ranches, amusement parks, and replacements for golf carts.[19]

    Major mini-truck manufacturers and their brands include: Daihatsu HijetHonda ActyTata AceMazda ScrumMitsubishi MinicabSubaru Sambar, and Suzuki Carry.

    Piaggio Porter in PalmeroSuzuki Carry in TaiwanTata Super Ace in Indonesia

    Light

    Light trucks are car-sized (in the US, no more than 13,900 lb (6.3 t)) and are used by individuals and businesses alike. In the EU they may not weigh more than 3.5 t (7,700 lb) and are allowed to be driven with a driving licence for cars.

    Pickup trucks, called utes in Australia and New Zealand, are common in North America and some regions of Latin America, Asia, and Africa, but not so in Europe, where this size of commercial vehicle is most often made as vans.

    Ford Ranger pickup truckLindner Unitrac 95L truck harvesting hay in SwitzerlandHolden Ute (VF) in Australia

    Medium

    Medium trucks are larger than light but smaller than heavy trucks. In the US, they are defined as weighing between 13,000 and 33,000 lb (5.9 and 15.0 t). For the UK and the EU the weight is between 3.5 and 7.5 t (7,700 and 16,500 lb). Local delivery and public service (dump trucksgarbage trucks and fire-fighting trucks) are normally around this size.

    Fuso Canter (8th gen) in TaiwanSML Isuzu in GhanaFire-fighting truck in Switzerland

    Heavy

    Heavy trucks are the largest on-road trucks, Class 8. These include vocational applications such as heavy dump trucks, concrete pump trucks, and refuse hauling, as well as ubiquitous long-haul 4×2 and 6×4 tractor units.[20]

    Road damage and wear increase very rapidly with the axle weight. The number of steering axles and the suspension type also influence the amount of the road wear. In many countries with good roads a six-axle truck may have a maximum weight of 44 t (97,000 lb) or more.

    cement mixer6×4 truck hauling a Walmart containerSeddon Atkinson Stratos refuse compactor

    Off-road

    Off-road trucks include standard, extra heavy-duty highway-legal trucks, typically outfitted with off-road features such as a front driving axle and special tires for applications such as logging and construction, and purpose-built off-road vehicles unconstrained by weight limits, such as the Liebherr T 282B mining truck.

    ALMA antenna transporter with 28 tires[21]Liebherr T 282B diesel-electric mining truck

    Maximum sizes by country

    Further information: Road train

    Mack Titan road train in Australia

    Australia has complex regulations over weight and length, including axle spacing, type of axle/axle group, rear overhang, kingpin to rear of trailer, drawbar length, ground clearance, as well as height and width laws. These limits are some of the highest in the world, a B-double can weigh 62.5 t (61.5 long tons; 68.9 short tons) and be 25 m (82 ft) long, and road trains used in the outback can weigh 172 t (169.3 long tons; 189.6 short tons) and be 53.5 m (176 ft) long.[22][23]

    The European Union also has complex regulations. The number and spacing of axles, steering, single or dual tires, and suspension type all affect maximum weights. Length of a truck, of a trailer, from axle to hitch point, kingpin to rear of trailer, and turning radius are all regulated. In additions, there are special rules for carrying containers, and countries can set their own rules for local traffic.[24]

    The United States Federal Bridge Law deals with the relation between the gross weight of the truck, the number of axles, the weight on and the spacing between the axles that the truck can have on the Interstate highway system.[25] Each State determines the maximum permissible vehiclecombination, and axle weight on state and local roads.

    CountryMaximum
    with three axles
    With one trailerMaximum combination
    Australia[22][23]23 t (22.6 long tons; 25.4 short tons)12 m (39 ft)172 t (169.3 long tons; 189.6 short tons)
    53.5 m (176 ft)
    China[26]25 t (24.6 long tons; 27.6 short tons)
    12 m (39 ft)
    49 t (48.2 long tons; 54.0 short tons)
    16.5 m (54 ft)
    55 t (54.1 long tons; 60.6 short tons)
    18.75 m (62 ft)
    EU[24]26 t (25.6 long tons; 28.7 short tons)
    12 m (39 ft)
    16.5 m (54 ft)44 t (43.3 long tons; 48.5 short tons)
    18.75 m (62 ft)
    Finland[27]28 t (27.6 long tons; 30.9 short tons)
    13 m (43 ft)
    76 t (74.8 long tons; 83.8 short tons)
    34.5 m (113 ft 2 in)
    76 t (74.8 long tons; 83.8 short tons)
    34.5 m (113 ft)
    Ireland[28]26 t (25.6 long tons; 28.7 short tons)
    12 m (39 ft)
    30 t (29.5 long tons; 33.1 short tons)
    16.5 m (54 ft 2 in)
    44 t (43.3 long tons; 48.5 short tons)
    22 m (72 ft)
    Sweden[29][30]26 t (25.6 long tons; 28.7 short tons)
    24 m (79 ft)
    74 t (72.8 long tons; 81.6 short tons)
    25.25 m (82 ft 10 in)
    74 t (72.8 long tons; 81.6 short tons)
    34.5 m (113 ft)
    UK[31]26 t (25.6 long tons; 28.7 short tons)
    12 m (39 ft)
    44 t (43.3 long tons; 48.5 short tons)
    16.5 m (54 ft)
    44 t (43.3 long tons; 48.5 short tons)
    18.75 m (62 ft)
    USA[32][33]
    (Interstate)
    54,000 lb (24 t)
    45 ft (13.7 m)
    80,000 lb (36 t)
    none
    80,000 lb (36 t)
    none

    Uniquely, the State of Michigan has a gross vehicle weight limit of 164,000 lb (74 t), which is twice the U.S. federal limit.[34][35][36] A measure to change the law was defeated in the Michigan Senate in 2019.[37][38][39][40][41]

    Design

    Almost all trucks share a common construction: they are made of a chassis, a cab, an area for placing cargo or equipment, axlessuspension and roadwheels, an engine and a drivetrainPneumatichydraulicwater, and electrical systems may also be present. Many also tow one or more trailers or semi-trailers.

    Cab

    A cabover truck
    Streamlined conventional cab
    Cab beside engine

    The “cab”, or “cabin” is an enclosed space where the driver is seated. A “sleeper” is a compartment attached to or integral with the cab where the driver can rest while not driving, sometimes seen in semi-trailer trucks.

    There are several cab configurations:

    • Cab over engine” (COE) or “flat nose”; where the driver is seated above the front axle and the engine. This design is almost ubiquitous in Europe, where overall truck lengths are strictly regulated, and is widely used in the rest of the world. They were common in North American heavy-duty trucks but lost prominence when permitted length was extended in the early 1980s. Nevertheless, this design is still popular in North America among medium- and light-duty trucks. To reach the engine, the whole cab tilts forward, earning this design the name of “tilt-cab”. This type of cab is especially suited to the delivery conditions in Europe where many roads require the short turning radius afforded by the shorter wheelbase of the cab over engine layout.[42]
    • “Cab-under” is where the driver is positioned at the front at the lowest point possible as means for maximum cargo space as possible.[43][44][45][46] Examples were made by Hunslet, Leyland, Bussing, Strick[47] and Steinwinter.[48]
    • “Conventional” cabs seated the driver behind the engine, as in most passenger cars or pickup trucks. Many new cabs are very streamlined, with a sloped hood (bonnet) and other features to lower drag. Conventional cabs are the most common in North America, Australia, and China, and are known in the UK as “American cabs”[citation needed] and in the Netherlands as “torpedo cabs”.[citation needed]
    • “Cab beside engine” designs are used for terminal tractors at shipping yards and for other specialist vehicles carrying long loads such as pipes. This type is often made by replacing the passenger side of a cab-over truck with an extended section of the load bed.

    A further step from this is the side loading forklift that can be described as a specially fabricated vehicle with the same properties as a truck of this type, in addition to the ability to pick up its own load.

    Engines and motors

    Cummins ISB 6.7L medium-duty truck diesel engine

    Most small trucks such as sport utility vehicles (SUVs), vans or pickups, and even light medium-duty trucks in North America, China, and Russia use gasoline engines (petrol engines), but many diesel engined models are now being produced. Most of the heavier trucks use four-stroke diesel engines with a turbocharger and intercooler. Huge off-highway trucks use locomotive-type engines such as a V12 Detroit Diesel two stroke engine. A large proportion of refuse trucks in the United States employ CNG (compressed natural gas) engines for their low fuel cost and reduced carbon emissions.

    A significant proportion of North American manufactured trucks use an engine built by the last remaining major independent engine manufacturer (Cummins) but most global OEMs such as Volvo Trucks and Daimler AG promote their own “captive” engines.[49]

    In the European Union, all new truck engines must comply with Euro VI emission regulations,[50] and Euro 7 from the late 2020s has stricter exhaust limits and also limits air pollution from brakes and tires.[51]

    As of 2019 several alternative technologies are competing to displace the use of diesel engines in heavy trucks. CNG engines are widely used in the US refuse industry and in concrete mixers, among other short-range vocations, but range limitations have prevented their broader uptake in freight hauling applications. Heavy electric trucks and hydrogen-powered trucks are new to the market in 2021,[52][53] but major freight haulers are interested.[54][55] Although cars will be first the phase-out of fossil fuel vehicles includes trucks.[56] According to The Economist magazine “Electric lorries will probably run on hydrogen, not batteries, which are too expensive.”[57] Other researchers say that once faster chargers are available batteries will become competitive against diesel for all, except perhaps the heaviest, trucks.[58]

    Drivetrain

    A truck rear suspension and drive axles overview
    Eaton Roadranger 18 speed “crash box” with automated gearshift

    Small trucks use the same type of transmissions as almost all cars, having either an automatic transmission or a manual transmission with synchromesh (synchronizers). Bigger trucks often use manual transmissions without synchronizers, saving bulk and weight, although synchromesh transmissions are used in larger trucks as well. Transmissions without synchronizers, known as “crash boxes”, require double-clutching for each shift, (which can lead to repetitive motion injuries), or a technique known colloquially as “floating”, a method of changing gears which does not use the clutch, except for starts and stops, due to the physical effort of double-clutching, especially with non-power-assisted clutches, faster shifts, and less clutch wear.

    Double-clutching allows the driver to control the engine and transmission revolutions to synchronize so that a smooth shift can be made; for example, when upshifting, the accelerator pedal is released and the clutch pedal is depressed while the gear lever is moved into neutral, the clutch pedal is then released and quickly pushed down again while the gear lever is moved to the next higher gear. Finally, the clutch pedal is released and the accelerator pedal pushed down to obtain the required engine speed. Although this is a relatively fast movement, perhaps a second or so while the transmission is in neutral, it allows the engine speed to drop and synchronize engine and transmission revolutions relative to the road speed. Downshifting is performed in a similar fashion, except the engine speed is now required to increase (while the transmission is in neutral) just the right amount in order to achieve the synchronization for a smooth, non-collision gear change. “Skip changing” is also widely used; in principle, the operation is the same as double-clutching, but it requires neutral be held slightly longer than a single-gear change.

    Common North American setups include 9, 10, 13, 15, and 18 speeds. Automatic and automated manual transmissions for heavy trucks are becoming more and more common, due to advances both in transmission and engine power. In Europe, 8, 10, 12, and 16 gears are common on larger trucks with a manual transmission, while conventional automatic or automated manual transmissions would have anything from 5 to 12 gears. Almost all heavy truck transmissions are of the “range and split” (double H shift pattern) type, where range change and so‑called half gears or splits are air operated and always preselected before the main gear selection.

    Frame

    A truck rear frame (chassis) section view
    Pickup truck frame (right rear view)

    A truck frame consists of two parallel boxed (tubular) or C‑shaped rails, or beams, held together by crossmembers. These frames are referred to as ladder frames due to their resemblance to a ladder if tipped on end. The rails consist of a tall vertical section (two if boxed) and two shorter horizontal flanges. The height of the vertical section provides opposition to vertical flex when weight is applied to the top of the frame (beam resistance). Though typically flat the whole length on heavy-duty trucks, the rails may sometimes be tapered or arched for clearance around the engine or over the axles. The holes in rails are used either for mounting vehicle components and running wires and hoses or measuring and adjusting the orientation of the rails at the factory or repair shop.

    The frame is usually made of steel, but can be made (whole or in part) of aluminum for a lighter weight. A tow bar may be found attached at one or both ends, but heavy tractors almost always make use of a fifth wheel hitch.[citation needed]

    Body types

    Box trucks have walls and a roof, making an enclosed load space. The rear has doors for unloading; a side door is sometimes fitted.[59]

    Chassis cab trucks have a fully enclosed cab at the front, with bare chassis frame-rails behind, suitable for subsequent permanent attachment of a specialized payload, like a fire-truck or ambulance body.

    Concrete mixers have a rotating drum on an inclined axis, rotating in one direction to mix, and in the other to discharge the concrete down chutes. Because of the weight and power requirements of the drum body and rough construction sites, mixers have to be very heavy duty.[60][61]

    Dual drive/Steer trucks are vehicles used to steer the rear of trailers.[62][63][64][65]

    Dump trucks (“tippers” in the UK) transport loose material such as sand, gravel, or dirt for construction. A typical dump truck has an open-box bed, which is hinged at the rear and lifts at the front, allowing the material in the bed to be unloaded (“dumped”) on the ground behind the truck.[66][67]

    Flatbed trucks have an entirely flat, level platform body. This allows for quick and easy loading but has no protection for the load. Hanging or removable sides are sometimes fitted,[68] often in the form of a stakebody.

    Refrigerator trucks have insulated panels as walls and a roof and floor, used for transporting fresh and frozen cargo such as ice cream, food, vegetables, and prescription drugs. They are mostly equipped with double-wing rear doors, but a side door is sometimes fitted.

    Refuse trucks have a specialized body for collecting and, often, compacting trash collected from municipal, commercial, and industrial sites. This application has the widest use of the cab-over configuration in North America, to provide better maneuverability in tight situations. They are also among the most severe-duty and highest GVWR trucks on public roads.

    Semi-tractors (“artics” in the UK) have a fifth wheel for towing a semi-trailer instead of a body.

    Tank trucks (“tankers” in the UK) are designed to carry liquids or gases. They usually have a cylindrical tank lying horizontally on the chassis. Many variants exist due to the wide variety of liquids and gases that can be transported.[69]

    Wreckers (“recovery lorries” in the UK) are used to recover and/or tow disabled vehicles. They are normally equipped with a boom with a cable; wheel/chassis lifts are becoming common on newer trucks.[70][71][72]

    Sales and sales issues

    Manufacturers

    Main article: List of truck manufacturers

    Truck market worldwide

    Pos.MakeUnits
    1Daimler AG (Mercedes-BenzFreightlinerUnimogWestern StarFusoBharatBenz)506,663[73]
    2Navistar International359,000[74]
    3Dongfeng336,869[75]
    4Tata317,780[76]
    5Volvo Group (VolvoMackRenaultUD Nissan)207,475[77]
    6Volkswagen Group (MANScaniaCaminhões e Ônibus)179,035[78]
    7Hino162,870[79]
    8Paccar (DAFKenworthPeterbiltLeyland)154,700[80]
    9Iveco140,200[81]

    Driving

    In many countries, driving a truck requires a special driving license. The requirements and limitations vary with each different jurisdiction.

    Australia

    Inside a Mack truck

    In Australia, a truck driver‘s license is required for any motor vehicle with a Gross Vehicle Mass (GVM) exceeding 4.5 t (4.4 long tons; 5.0 short tons). The motor vehicles classes are further expanded as:Combination

    • HC: Heavy Combination, a typical prime mover plus semi-trailer combination.
    • MC: Multi Combination, e.g., B Doubles/road trains

    Rigid

    • LR: Light rigid: a rigid vehicle with a GVM of more than 4.5 t (4.4 long tons; 5.0 short tons) but not more than 8 t (7.9 long tons; 8.8 short tons). Any towed trailer must not weigh more than 9 t (8.9 long tons; 9.9 short tons) GVM.
    • MR: Medium rigid: a rigid vehicle with 2 axles and a GVM of more than 8 t (7.9 long tons; 8.8 short tons). Any towed trailer must not weigh more than 9 t (8.9 long tons; 9.9 short tons) GVM. Also includes vehicles in class LR.
    • HR: Heavy Rigid: a rigid vehicle with three or more axles and a GVM of more than 8 t (7.9 long tons; 8.8 short tons). Any towed trailer must not weigh more than 9 t (8.9 long tons; 9.9 short tons) GVM. Also includes articulated buses and vehicles in class MR.

    Heavy vehicle transmission

    There is also a heavy vehicle transmission condition for a license class HCHR, or MC test passed in a vehicle fitted with an automatic or synchromesh transmission; a driver’s license will be restricted to vehicles of that class fitted with a synchromesh or automatic transmission. To have the condition removed, a person needs to pass a practical driving test in a vehicle with non-synchromesh transmission (constant mesh or crash box).[82]

    Europe

    Inside a Mercedes-Benz truck

    Driving licensing has been harmonized throughout the European Union and the EEA (and practically all European non-member states), so that common rules apply within Europe (see European driving licence). As an overview, to drive a vehicle weighing more than 7.5 t (7.4 long tons; 8.3 short tons) for commercial purposes requires a specialist license (the type varies depending on the use of the vehicle and number of seats). For licenses first acquired after 1997, that weight was reduced to 3.5 t (3.4 long tons; 3.9 short tons), not including trailers.[citation needed]

    Since 2013, the C1 license category allows driving vehicles over 3.5 and up to 7.5 tonnes. The C license category allows driving vehicles over 3.5 tonnes with a trailer up to 750 kg, and the CE category allows driving category C vehicles with a trailer over 750 kg.

    South Africa

    To drive any vehicle with a GVM exceeding 3.5 t (3.4 long tons; 3.9 short tons), a code C1 drivers license is required. Furthermore, if the vehicle exceeds 16 t (15.7 long tons; 17.6 short tons) a code C license becomes necessary.

    To drive any vehicle in South Africa towing a trailer with a GVM more than 7.5 t (7.4 long tons; 8.3 short tons), further restrictions apply and the driver must possess a license suitable for the GVM of the total combination as well as an articulated endorsement. This is indicated with the letter “E” prefixing the license code.

    In addition, any vehicle designed to carry goods or passengers may only be driven by a driver possessing a Public Driver’s Permit, (or PrDP) of the applicable type. This is an additional license that is added to the DL card of the operator and subject to annual renewal unlike the five-year renewal period of a normal license.

    The requirements for obtaining the different classes are below.

    • “G”: Required for the transport of general goods, requires a criminal record check and a fee on issuing and renewal.
    • “P”: Required for the transport of paying passengers, requires a more stringent criminal record check, additionally the driver must be over the age of 21 at time of issue. A G class PrDP will be issued at the same time.
    • “D”: Required for the transport of dangerous materials, requires all of the same checks as class P., and in addition the driver must be over 25 at time of issue.

    United States

    Inside a Navistar 9000

    In the United States, a commercial driver’s license is required to drive any type of commercial vehicle weighing 26,001 lb (11,794 kg) or more.[83] The federal government regulates how many hours a driver may be on the clock, how much rest and sleep time is required (e.g., 11 hours driving/14 hours on-duty followed by 10 hours off, with a maximum of 70 hours/8 days or 60 hours/7 days, 34 hours restart )[84] Violations are often subject to significant penalties. Instruments to track each driver’s hours must sometimes be fitted. In 2006, the US trucking industry employed 1.8 million drivers of heavy trucks.[85]

    There is a shortage of willing trained long-distance truck drivers.[86] Part of the reason for this is the economic fallout from deregulation of the trucking industry. Michael H. Belzerassociate professor, in the economics department at Wayne State University and co-author of Sweatshops on Wheels: Winners and Losers in Trucking Deregulation, argues that low pay, bad working conditions and unsafe conditions have been a direct result of deregulation.[87][88] The book cites poor working conditions and an unfair pay system as responsible for high annual employee turnover in the industry.[89][90]

    In 2018, in the US, 5,096 large trucks and buses were involved in fatal crashes:

    • The number of large trucks involved in fatal crashes is 4,862,
    • The number of large trucks involved in injury crashes is 112,000,
    • The number of large trucks involved in property damage only crashes is 414,000.[91]

    Environmental effects

    See also: Diesel exhaust and Environmental effects of transport

    Exhaust fumes from a small truck
    Trucks’ share of US vehicles produced, has tripled since 1975. Though vehicle fuel efficiency has increased within each category, the overall trend toward trucks has offset some of the benefits of greater fuel economy and reductions in pollution and carbon dioxide emissions.[92] Without the shift towards SUVs, energy use per unit distance could have fallen 30% more than it did from 2010 to 2022.[93]

    Like cars, trucks contribute to air, noise, and water pollution.[94] Unlike cars, as of 2022, most trucks run on diesel, and diesel exhaust is especially dangerous for health.[95] Some countries outside the EU have different vehicle emission standards for trucks and cars.[96][97]

    NOx and particulates emitted by trucks are very dangerous to health,[98][99] causing thousands of early deaths annually in the US alone.[100] As older trucks are usually the worst,[101] many cities have banned 20th century trucks.[102] Air pollution also threatens professional truck drivers.[103]

    Over a quarter of global transport CO2 emissions are from road freight,[104] in 2021 over 1700 million tonnes from medium and heavy trucks,[105] so many countries are further restricting truck CO2 emissions to help limit climate change.[106] Many environmental organizations favor laws and incentives to encourage the switch from road to rail, especially in Europe.[107] Several countries have pledged that 30% of sales of trucks and buses will be zero emission by 2030.[108]

    With respect to noise pollution, trucks emit considerably higher sound levels at all speeds compared to typical cars; this contrast is particularly strong with heavy-duty trucks.[109] There are several aspects of truck operations that contribute to the overall sound that is emitted. Continuous sounds are those from tires rolling on the roadway and the constant hum of their diesel engines at highway speeds. Less frequent noises, but perhaps more noticeable, are things like the repeated sharp-pitched whistle of a turbocharger on acceleration, or the abrupt blare of an exhaust brake retarder when traversing a downgrade. There has been noise regulation put in place to help control where and when the use of engine braking retarders are allowed.[citation needed]

    Operator health and safety

    An orange metal housing with an open panel containing three horizontal stacked filters
    Truck cab filter housing using a contiguous series of pre-, HEPA, and charcoal panel filters

    A truck cab is a hazard control that protects the truck operator from hazardous airborne pollutants.[citation needed] As an enclosure, it is an example of an engineering control. Enclosed operator cabs have been used on agriculture, mining, and construction vehicles for several decades. Most modern-day enclosed cabs have heating, ventilation, and air conditioning (HVAC) systems for primarily maintaining a comfortable temperature and providing breathable air for their occupants. Various levels of filtration can be incorporated into the HVAC system to remove airborne pollutants such as dusts, diesel particulate matter (DPM), and other aerosols.[110]

    Two key elements of an effective environmental enclosure are a good filtration system and an enclosure with good integrity (sealed isolation from the outside environment). It is recommended that a filtration system filter out at least 95% or greater of airborne respirable aerosols from the intake airflow, with an additional recirculation filtering component for the inside air. Good enclosure integrity is also needed to achieve positive pressure to prevent wind-driven aerosol penetration into the enclosure, as well as to minimize air leakage around the filtration system. Test methods and mathematical modeling of environmental enclosures are also beneficial for quantifying and optimizing filtration system designs, as well as maintaining optimum protection factor performance for enclosure occupants.[110]

    Operations issues

    Taxes

    Commercial trucks in the US pay higher road use taxes on a state level than other road vehicles and are subject to extensive regulation.[111] A few reasons commercial trucks pay higher road use taxes: they are bigger and heavier than most other vehicles, and cause more wear and tear per hour on roadways; and trucks and their drivers are on the road for more hours per day. Rules on use taxes differ among jurisdictions.

    Damage to pavement

    The life of a pavement is measured by the number of passes of a vehicle axle. It may be evaluated using the Load Equivalency Factor,[112] which states that the damage by the pass of a vehicle axle is proportional to the 4th power of the weight, so a ten-ton axle consumes 10,000 times the life of the pavement as a one-ton axle. For that reason, loaded trucks cost the same as thousands of cars in pavement costs, and are subject to higher taxes and highway tolls.[38][39]

    Safety

    Globe icon.The examples and perspective in this section deal primarily with the United States and Europe and do not represent a worldwide view of the subject. You may improve this section, discuss the issue on the talk page, or create a new section, as appropriate. (August 2024) (Learn how and when to remove this message)

    Trucking accidents

    Trucking accident

    In 2002 and 2004, there were over 5,000 fatalities related to trucking accidents in the United States. The trucking industry has since made significant efforts in increasing safety regulations. In 2008, the industry had successfully lowered the fatality rate to just over 4,000 deaths, but trucking accidents are still an issue that causes thousands of deaths and injuries each year. Approximately 6,000 trucking accident fatalities occur annually in the United States. Fatalities are not the only issue caused by trucking accidents. Here are some of the environmental issues that arise with trucking accidents:

    • 14.4% of trucking accidents cause cargo to spill
    • 6.5% cause open flames

    Following increased pressure from The Times “Cities Fit For Cycling” campaign and from other media in Spring 2012, warning signs are now displayed on the backs of many heavy goods vehicles (HGV). These signs are directed against a common type of accident that occurs when the large vehicle turns left at a junction: a cyclist trying to pass on the nearside can be crushed against the HGV’s wheels, especially if the driver cannot see the cyclist. The signs, such as the winning design of the InTANDEM road safety competition[usurped] launched in March 2012, advocate extra care when passing a large vehicle on the nearside.

    HGV safety in the EU

    In-vehicle speed limitation is required applying a 90 km/h limit to commercial vehicles over 3.5 tonnes.[113]

    Front, side, and rear underrun protection is required on commercial vehicles over 3.5 tonnes.[113]

    Trucks must be fitted with blind-spot mirrors that give drivers a wider field of vision than conventional mirrors.

  • Salt

    In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as rock salt or halite. Salt is essential for life in general (being the source of the essential dietary minerals sodium and chlorine), and saltiness is one of the basic human tastes. Salt is one of the oldest and most ubiquitous food seasonings, and is known to uniformly improve the taste perception of food, including otherwise unpalatable food.[1] Saltingbrining, and pickling are ancient and important methods of food preservation.

    Some of the earliest evidence of salt processing dates to around 6000 BC, when people living in the area of present-day Romania boiled spring water to extract salts; a salt works in China dates to approximately the same period.[2] Salt was prized by the ancient HebrewsGreeksRomansByzantinesHittitesEgyptians, and Indians. Salt became an important article of trade and was transported by boat across the Mediterranean Sea, along specially built salt roads, and across the Sahara on camel caravans. The scarcity and universal need for salt have led nations to go to war over it and use it to raise tax revenues. For example, the El Paso Salt War which took place in El Paso in the late 1860.[3] Salt is used in religious ceremonies and has other cultural and traditional significance.

    Salt is processed from salt mines, and by the evaporation of seawater (sea salt) and mineral-rich spring water in shallow pools. The greatest single use for salt (sodium chloride) is as a feedstock for the production of chemicals.[4] It is used to produce caustic soda and chlorine, and in the manufacture of products such as polyvinyl chlorideplastics, and paper pulp. Of the annual global production of around three hundred million tonnes, only a small percentage is used for human consumption. Other uses include water conditioning processes, de-icing highways, and agricultural use.[5][6] Edible salt is sold in forms such as sea salt and table salt, the latter of which usually contains an anti-caking agent and may be iodised to prevent iodine deficiency. As well as its use in cooking and at the table, salt is present in many processed foods.

    Sodium is an essential element for human health via its role as an electrolyte and osmotic solute.[7][8][9] However, excessive salt consumption increases the risk of cardiovascular diseases such as hypertension. Such health effects of salt have long been studied. Accordingly, numerous world health associations and experts in developed countries recommend reducing consumption of popular salty foods.[9][10] The World Health Organization recommends that adults consume less than 2,000 mg of sodium, equivalent to 5 grams of salt, per day.[11][12]

    History

    Main article: History of salt

    Salt production in Halle, Saxony-Anhalt (1670)
    Ponds near Maras, Peru, fed from a mineral spring and used for salt production since pre-Inca times

    All through history, the availability of salt has been pivotal to civilization. What is now thought to have been the first city in Europe is Solnitsata, in Bulgaria, which was a salt mine, providing the area now known as the Balkans with salt since 5400 BC.[13] Salt was the best-known food preservative, especially for meat, for many thousands of years.[14] A very ancient salt-works operation has been discovered at the Poiana Slatinei archaeological site next to a salt spring in LuncaNeamț County, Romania. Evidence indicates that Neolithic people of the Precucuteni Culture were boiling the salt-laden spring water through the process of briquetage to extract salt as far back as 6050 BC.[15] The salt extracted from this operation may have directly correlated with the rapid growth of this society’s population soon after production began.[16] The harvest of salt from the surface of Xiechi Lake near Yuncheng in Shanxi, China, dates back to at least 6000 BC, making it one of the oldest verifiable saltworks.[17]

    There is more salt in animal tissues, such as meat, blood, and milk, than in plant tissues.[18] Nomads who subsist on their flocks and herds do not eat salt with their food, but agriculturalists, feeding mainly on cereals and vegetable matter, need to supplement their diet with salt.[19] With the spread of civilization, salt became one of the world’s main trading commodities. It was of high value to the ancient Hebrews, the Greeks, the Romans, the Byzantines, the Hittites and other peoples of antiquity. In the Middle East, salt was used to seal an agreement ceremonially, and the ancient Hebrews made a “covenant of salt” with God and sprinkled salt on their offerings to show their trust in him.[20] An ancient practice in time of war was salting the earth: scattering salt around in a defeated city to symbolically prevent plant growth. The Bible tells the story of King Abimelech who was ordered by God to do this at Shechem,[21] and various texts claim that the Roman general Scipio Aemilianus Africanus ploughed over and sowed the city of Carthage with salt after it was defeated in the Third Punic War (146 BC),[22] although this story is now considered to be entirely apocryphal.

    Salt may have been used for barter in connection with the obsidian trade in Anatolia in the Neolithic Era.[23] Salt was included among funeral offerings found in ancient Egyptian tombs from the third millennium BC, as were salted birds, and salt fish.[24] From about 2800 BC, the Egyptians began exporting salt fish to the Phoenicians in return for Lebanon cedar, glass, and the dye Tyrian purple; the Phoenicians traded Egyptian salted fish and salt from North Africa throughout their Mediterranean trade empire.[25] Herodotus described salt trading routes across Libya back in the 5th century BC. In the early years of the Roman Empire, roads were built for the transportation of salt from the salt imported at Ostia to the capital.[26]

    In Africa, salt was used as currency south of the Sahara, and slabs of rock salt were used as coins in Abyssinia.[19] The Tuareg have traditionally maintained routes across the Sahara especially for the transportation of salt by Azalai (salt caravans). The caravans still cross the desert from southern Niger to Bilma, although much of the trade now takes place by truck. Each camel takes two bales of fodder and two of trade goods northwards and returns laden with salt pillars and dates.[27] In Gabon, before the arrival of Europeans, the coast people carried on a remunerative trade with those of the interior by the medium of sea salt. This was gradually displaced by the salt that Europeans brought in sacks, so that the coast natives lost their previous profits; as of the late 1950s, sea salt was still the currency best appreciated in the interior.[28]

    SalzburgHallstatt, and Hallein lie within 17 km (11 mi) of each other on the river Salzach in central Austria in an area with extensive salt deposits. Salzach means “salt river” while Salzburg means “salt castle”, both taking their names from the German word Salz, salt. Hallstatt was the site of the world’s first salt mine.[29] The town gave its name to the Hallstatt culture that began mining for salt in the area in about 800 BC. Around 400 BC, the townsfolk, who had previously used pickaxes and shovels, began open pan salt making. During the first millennium BC, Celtic communities grew rich trading salt and salted meat to Ancient Greece and Ancient Rome in exchange for wine and other luxuries.[14]

    The word salary comes from the Latin word for salt. The reason for this is unknown; a persistent modern claim that the Roman Legions were sometimes paid in salt is baseless.[30][31] The word salad literally means “salted”, and comes from the ancient Roman practice of salting leaf vegetables.[32]

    Wars have been fought over salt. Venice won a war with Genoa over the product, and it played a role in the American Revolution. Cities on overland trade routes grew rich by levying duties,[33] and towns like Liverpool flourished on the export of salt extracted from the salt mines of Cheshire.[34] Various governments have at different times imposed salt taxes on their peoples. The voyages of Christopher Columbus are said to have been financed from salt production in southern Spain, and the oppressive salt tax in France was one of the causes of the French Revolution. After being repealed, this tax was reimposed by Napoleon when he became emperor to pay for his foreign wars, and was not finally abolished until 1946.[33] In 1930, Mahatma Gandhi led a crowd of 100,000 protestors on the “Dandi March” or “Salt Satyagraha“, during which they made their own salt from the sea as a demonstration of their opposition to the colonial salt tax. This act of civil disobedience inspired numerous Indians and transformed the Indian independence movement into a national struggle.[35]

    Physical properties

    Main article: Sodium chloride

    SEM image of a grain of table salt

    Salt is mostly sodium chloride (NaCl). Sea salt and mined salt may contain trace elements. Mined salt is often refined. Salt crystals are translucent and cubic in shape; they normally appear white but impurities may give them a blue or purple tinge. When dissolved in water sodium chloride separates into Na+ and Cl ions, and the solubility is 359 grams per litre.[36] From cold solutions, salt crystallises as the dihydrate NaCl·2H2O. Solutions of sodium chloride have very different properties from those of pure water; the freezing point is −21.12 °C (−6.02 °F) for 23.31 wt% of salt, and the boiling point of saturated salt solution is around 108.7 °C (227.7 °F).[4]

    Edible salt

    See also: List of edible salts and Salt substitute

    Comparison of table salt with kitchen salt. Shows a typical salt shaker and salt bowl with salt spread before each on a black background.

    Salt is essential to the health of humans and other animals, and it is one of the five basic taste sensations.[37] Salt is used in many cuisines, and it is often found in salt shakers on diners’ eating tables for their personal use on food. Salt is also an ingredient in many manufactured foodstuffs. Table salt is a refined salt containing about 97 to 99 percent sodium chloride.[38][39][40] Usually, anticaking agents such as sodium aluminosilicate or magnesium carbonate are added to make it free-flowing. Iodized salt, containing potassium iodide, is widely available. Some people put a desiccant, such as a few grains of uncooked rice[41] or a saltine cracker, in their salt shakers to absorb extra moisture and help break up salt clumps that may otherwise form.[42]

    Fortified table salt

    Some table salt sold for consumption contains additives that address a variety of health concerns, especially in the developing world. The identities and amounts of additives vary from country to country. Iodine is an important micronutrient for humans, and a deficiency of the element can cause lowered production of thyroxine (hypothyroidism) and enlargement of the thyroid gland (endemic goitre) in adults or cretinism in children.[43] Iodized salt has been used to correct these conditions since 1924[44] and consists of table salt mixed with a minute amount of potassium iodidesodium iodide, or sodium iodate. A small amount of dextrose may be added to stabilize the iodine.[45] Iodine deficiency affects about two billion people around the world and is the leading preventable cause of intellectual disabilities.[46] Iodized table salt has significantly reduced disorders of iodine deficiency in countries where it is used.[47]

    The amount of iodine and the specific iodine compound added to salt varies. In the United States, the Food and Drug Administration (FDA) recommends 150 micrograms of iodine per day for both men and women.[48] US iodized salt contains 46–77 ppm (parts per million), whereas in the UK the recommended iodine content of iodized salt is 10–22 ppm.[49]

    Sodium ferrocyanide, yellow prussiate of soda, is sometimes added to salt as an anticaking agent.[50] Such anticaking agents have been added since at least 1911 when magnesium carbonate was first added to salt to make it flow more freely.[51] The safety of sodium ferrocyanide as a food additive was found to be provisionally acceptable by the Committee on Toxicity in 1988.[50] Other anticaking agents sometimes used include tricalcium phosphatecalcium or magnesium carbonates, fatty acid salts (acid salts), magnesium oxidesilicon dioxidecalcium silicate, sodium aluminosilicate and calcium aluminosilicate. Both the European Union and the United States Food and Drug Administration permitted the use of aluminium in the latter two compounds.[52]

    In “doubly fortified salt”, both iodide and iron salts are added. The latter alleviates iron deficiency anaemia, which interferes with the mental development of an estimated 40% of infants in the developing world. A typical iron source is ferrous fumarate.[4] Another additive, especially important for pregnant women, is folic acid (vitamin B9), which gives the table salt a yellow colour. Folic acid helps prevent neural tube defects and anaemia, which affect young mothers, especially in developing countries.[4]

    A lack of fluoride in the diet is the cause of a greatly increased incidence of dental caries.[53] Fluoride salts can be added to table salt with the goal of reducing tooth decay, especially in countries that have not benefited from fluoridated toothpastes and fluoridated water. The practice is more common in some European countries where water fluoridation is not carried out. In France, 35% of the table salt sold contains added sodium fluoride.[4]

    Other kinds

    Himalayan salt is halite with a distinct pink colour.

    Salt deposits beside the Dead Sea, Israel

    Unrefined sea salt contains small amounts of magnesium and calcium halides and sulfates, traces of algal products, salt-resistant bacteria and sediment particles. The calcium and magnesium salts confer a faintly bitter overtone, and they make unrefined sea salt hygroscopic (i.e., it gradually absorbs moisture from air if stored uncovered). Algal products contribute a mildly “fishy” or “sea-air” odour, the latter from organobromine compounds. Sediments, the proportion of which varies with the source, give the salt a dull grey appearance. Since taste and aroma compounds are often detectable by humans in minute concentrations, sea salt may have a more complex flavour than pure sodium chloride when sprinkled on top of food. When salt is added during cooking however, these flavours would likely be overwhelmed by those of the food ingredients.[54] The refined salt industry cites scientific studies saying that raw sea and rock salts do not contain enough iodine salts to prevent iodine deficiency diseases.[55]

    Salts have diverse mineralities depending on their source, giving each a unique flavour. Fleur de sel, a natural sea salt from the surface of evaporating brine in salt pans, has a distinctive flavour varying with its source. In traditional Korean cuisine, so-called “bamboo salt” is prepared by roasting salt[56] in a bamboo container plugged with mud at both ends. This product absorbs minerals from the bamboo and the mud, and has been claimed to increase the anticlastogenic and antimutagenic properties of doenjang (a fermented bean paste).[57] Kosher or kitchen salt has a larger grain size than table salt and is used in cooking. It can be useful for brining, in bread or pretzel making, and as a scrubbing agent when combined with oil.[58]

    Salt in food

    Salt is present in most foods, but in naturally occurring foodstuffs such as meats, vegetables and fruit, it is present in very small quantities. It is often added to processed foods (such as canned foods and especially salted foodspickled foods, and snack foods or other convenience foods), where it functions as both a preservative and a flavouringDairy salt is used in the preparation of butter and cheese products.[59] As a flavouring, salt enhances the taste of other foods by suppressing the bitterness of those foods making them more palatable and relatively sweeter.[60]

    Before the advent of electrically powered refrigeration, salting was one of the main methods of food preservation. Thus, herring contains 67 mg sodium per 100 g, while kipper, its preserved form, contains 990 mg. Similarly, pork typically contains 63 mg while bacon contains 1,480 mg, and potatoes contain 7 mg but potato crisps 800 mg per 100 g.[18] Salt is used extensively in cooking as a flavouring, and in cooking techniques such as with salt crusts and brining. The main sources of salt in the Western diet, apart from direct use, are bread and cereals, meat, and dairy products.[18]

    In many East Asian cultures, salt is not traditionally used as a condiment.[61] In its place, condiments such as soy saucefish sauce and oyster sauce tend to have a high sodium content and fill a similar role to table salt in western cultures. They are most often used for cooking rather than as table condiments.[62]

    Biology of salt taste

    See also: Taste receptor § Salt, and Taste § Saltiness

    Human salt taste is detected by sodium taste receptors present in taste bud cells on the tongue.[63] Human sensory taste testing studies have shown that proteolyzed forms of epithelial sodium channel (ENaC) function as the human salt taste receptor.[64]

    Sodium consumption and health

    Main article: Health effects of salt

    Table salt is made up of just under 40% sodium by weight, so a 6 g serving (1 teaspoon) contains about 2,400 mg of sodium.[65] Sodium serves a vital purpose in the human body: via its role as an electrolyte, it helps nerves and muscles to function correctly, and it is one factor involved in the osmotic regulation of water content in body organs (fluid balance).[66] Most of the sodium in the Western diet comes from salt.[9] The habitual salt intake in many Western countries is about 10 g per day, and it is higher than that in many countries in Eastern Europe and Asia.[67] The high level of sodium in many processed foods has a major impact on the total amount consumed.[68] In the United States, 75% of the sodium eaten comes from processed and restaurant foods, 11% from cooking and table use and the rest from what is found naturally in foodstuffs.[69]

    Because consuming too much sodium increases risk of cardiovascular diseases,[9] health organizations generally recommend that people reduce their dietary intake of salt.[9][11][70][71] High sodium intake is associated with a greater risk of stroke, total cardiovascular disease and kidney disease.[8][67] A reduction in sodium intake by 1,000 mg per day may reduce cardiovascular disease by about 30 percent.[7][9] In adults and children with no acute illness, a decrease in the intake of sodium from the typical high levels reduces blood pressure.[70][72] A low sodium diet results in a greater improvement in blood pressure in people with hypertension.[73][74]

    The World Health Organization recommends that adults should consume less than 2,000 mg of sodium (which is contained in 5 g of salt) per day.[11] Guidelines by the United States recommend that people with hypertension, African Americans, and middle-aged and older adults should limit consumption to no more than 1,500 mg of sodium per day and meet the potassium recommendation of 4,700 mg/day with a healthy diet of fruits and vegetables.[9][75]

    While reduction of sodium intake to less than 2,300 mg per day is recommended by developed countries,[9] one review recommended that sodium intake be reduced to at least 1,200 mg (contained in 3 g of salt) per day, as a further reduction in salt intake led to a greater fall in systolic blood pressure for all age groups and ethnicities.[70] Another review indicated that there is inconsistent/insufficient evidence to conclude that reducing sodium intake to lower than 2,300 mg per day is either beneficial or harmful.[76]

    Evidence shows a more complicated relationship between salt and cardiovascular disease. “The association between sodium consumption and cardiovascular disease or mortality is U-shaped, with increased risk at both high and low sodium intake.”[77] The findings showed that increased mortality from excessive salt intake was primarily associated with individuals with hypertension. The levels of increased mortality among those with restricted salt intake appeared to be similar regardless of blood pressure. This evidence shows that while those with hypertension should primarily focus on reducing sodium to recommended levels, all groups should seek to maintain a healthy level of sodium intake of between 4 and 5 grams (equivalent to 10-13 g salt) a day.[77]

    One of the two most prominent dietary risks for disability in the world are diets high in sodium.[78]

    Non-dietary uses

    Main article: Sodium chloride

    Only a small percentage of the salt manufactured in the world is used in food. The remainder is used in agriculture, water treatment, chemical production, de-icing, and other industrial use cases.[4] In the practice of watering plants with salt as a fertilizer, applying a moderate concentration helps avoid potential toxicity; typically, 1–3 grams (0.035–0.106 oz) per liter is considered safe and effective for most plants.[79][80][81] Sodium chloride is one of the largest volume inorganic raw materials. It is a feedstock in the production of caustic soda and chlorine. These are used in the manufacture of PVCpaper pulp and many other inorganic and organic compounds. Salt is used as a flux in the production of aluminium. For this purpose, a layer of melted salt floats on top of the molten metal and removes iron and other metal contaminants. It is used in the manufacture of soaps and glycerine, where it is used to saponify fats. As an emulsifier, salt is used in the manufacture of synthetic rubber, and another use is in the firing of pottery, when salt added to the furnace vaporises before condensing onto the surface of the ceramic material, forming a strong glaze.[82]

    When drilling through loose materials such as sand or gravel, salt may be added to the drilling fluid to provide a stable “wall” to prevent the hole collapsing. There are many other processes in which salt is involved. These include its use as a mordant in textile dying, to regenerate resins in water softening, for the tanning of hides, the preservation of meat and fish and the canning of meat and vegetables.[82][83][84]

    Production

    See also: List of countries by salt production

    Sifto Canada salt mine and processing plant at the harbor in Goderich, Ontario, Canada

    Food-grade salt accounts for only a small part of salt production in industrialized countries (7% in Europe),[85] although worldwide, food uses account for 17.5% of total production.[86] In 2018, total world production of salt was 300 million tonnes, the top six producers being China (68 million), the United States (42 million), India (29 million), Germany (13 million), Canada (13 million) and Australia (12 million).[87]

    The manufacture of salt is one of the oldest chemical industries.[88] A major source of salt is seawater, which has a salinity of approximately 3.5%.[4] This means that there are about 35 g (1.2 oz) of dissolved salts, predominantly sodium (Na+
    ) and chloride (Cl
    ions, per kilogram (2.2 lbs) of water.[89] The world’s oceans are a virtually inexhaustible source of salt, and this abundance of supply means that reserves have not been calculated.[83] The evaporation of seawater is the production method of choice in marine countries with high evaporation and low precipitation rates. Salt evaporation ponds are filled from the ocean and salt crystals can be harvested as the water dries up. Sometimes these ponds have vivid colours, as some species of algae and other micro-organisms thrive in conditions of high salinity.[90]

    Away from the sea, salt is extracted from the vast sedimentary deposits which have been laid down over the millennia from the evaporation of seas and lakes. These sources are either mined directly, producing rock salt, or are extracted by pumping water into the deposit. In either case, the salt may be purified by mechanical evaporation of brine. Traditionally, purification was achieved in shallow open pans that were heated to accelerate evaporation. Vacuum-based methods are also employed.[84] The raw salt is refined by treatment with chemicals that precipitate most impurities (largely magnesium and calcium salts). Multiple stages of evaporation are then applied.[91] Some salt is produced using the Alberger process, which involves vacuum pan evaporation combined with the seeding of the solution with cubic crystals, and produces a grainy-type flake.[92] The Ayoreo, an indigenous group from the Paraguayan Chaco, obtain their salt from the ash produced by burning the timber of the Indian salt tree (Maytenus vitis-idaea) and other trees.[93]

    The largest mine operated by underground workings in the world is the Sifto mine, located mostly 550 meters below Lake Huron, in Goderich, Ontario (Canada). About seven million tons of salt are extracted from it annually.[94] The Khewra Salt Mine in Pakistan has nineteen storeys, eleven of which are underground, and 400 km (250 mi) of passages. The salt is dug out by the room and pillar method, where about half the material is left in place to support the upper levels. Extraction of Himalayan salt is expected to last 350 years at the present rate of extraction of around 385,000 tons per annum.The mine is also a major tourist attraction, receiving around a quarter of a million visitors a year.[95]

    In religion

    Bread and salt at a Russian wedding ceremony

    Salt has long held an important place in religion and culture. At the time of Brahmanic sacrifices, in Hittite rituals and during festivals held by Semites and Greeks at the time of the new moon, salt was thrown into a fire where it produced crackling noises.[96] The ancient Egyptians, Greeks and Romans invoked their gods with offerings of salt and water and some people think this to be the origin of Holy Water in the Christian faith.[97] In Judaism, it is recommended to have either a salty bread or to add salt to the bread if this bread is unsalted when doing Kiddush for Shabbat. It is customary to spread some salt over the bread or dip it in a little salt when passing it around the table after the Kiddush.[98] To preserve the covenant between their people and God, Jews dip the Sabbath bread in salt.[97] Salt plays a role within different Christian traditions. It is mandatory in the rite of the Tridentine Mass.[99] Salt is used in the third item (which includes an Exorcism) of the Celtic Consecration (cf. Gallican Rite) that is employed in the consecration of a church, and it is permitted to be added to the water “where it is customary” in the Roman Catholic rite of Holy water.[99] The Bible makes multiple mentions of salt, both of the mineral itself and as a metaphor. Uses include the tale of how Lot’s wife is turned into a pillar of salt when looking back at the cities of Sodom and Gomorrah as they are destroyed. In the New TestamentJesus refers to his followers as the “salt of the earth“.[100]

    In Aztec mythology, Huixtocihuatl was a fertility goddess who presided over salt and salt water.[101] Salt is an auspicious substance in Hinduism and is used in ceremonies like house-warmings and weddings.[102] In Jainism, devotees lay an offering of raw rice with a pinch of salt before a deity to signify their devotion and salt is sprinkled on a person’s cremated remains before the ashes are buried.[103] Salt is believed to ward off evil spirits in Mahayana Buddhist tradition. When returning home from a funeral, a pinch of salt is thrown over the left shoulder as this prevents evil spirits from entering the house.[104] In ShintoShio (, lit. “salt”) is used for ritual purification of locations and people (harae, specifically shubatsu), and small piles of salt are placed in dishes by entrances to ward off evil and to attract patrons.