The fourth-generation Toyota Prius is manufactured at the company's Tsutsumi plant, a few kilometres south-east of Nagoya, around 100 minutes from Tokyo by Shinkansen bullet train. From Tsutsumi's viewing gantries, two production lines stretch away into the distance. These halls house the trim workshop. Here, completed body shells roll in, are divested of their doors (which make their way in pairs along a separate line) and the interior, hybrid system, dashboard and seats are installed. The factory, which has been making Priuses since 2003, produces 430,000 cars a year. From 6.30am to 1am, it can turn out a Prius every minute.

This is the Toyota Production System (TPS) at work, a fabled refinement that funnels the immense complexity of car-making into a series of simple stages. Each step is serviced using the just-in-time manufacturing process by the requisite parts supplier. The system is controlled by the workers themselves, who have autonomy over stopping and starting the line to resolve issues.

TPS is a mainstay of business-school case studies, as well as being widely imitated by envious rivals. The system is about efficiency in all its forms, from the constant tracking of components (kanban) to the fault-reporting system (andon), which dates back to Toyota Industries founder Sakichi Toyoda's early days making looms. The process of constant improvement is known as kaizen. Toyota has this down to a fine art, employing kaizen teams to roam the factory and scout for potential problems and possible efficiencies. On posters, shirts and tabards, the plant's official mascot - a cartoon horse called Tsutsuma-Kun - preaches health and safety.


In the adjoining building, stamped-steel Prius bodies are assembled robotically, using conventional welding and lasers (as well as a secret proprietary method that WIRED wasn't allowed to photograph). Today, the 1,850 robots at Tsutsumi are sourced from one of three main suppliers: Nachi, Yaskawa and Kawasaki. As the body shells roll into position, a cluster of around ten closely spaced robotic arms swivel and pivot in a synchronised dance that is simultaneously beguiling, awe-inspiring and terrifying. Then they all lurch forward at once, finding the pinch points where two pieces join, then dab and squeeze their welding pincers along the seams to seal them. Each stage takes just under a minute, before the arms retract and the line rolls on. Large components are sent straight to the line by a system of overhead wires and gravity-driven palettes. At the same time, a constant stream of electric trains bring the rest along a miniature road system of intersections and stop signs. The building is a chorus of whirring ratchets, beeping trucks, buzzing drills, the rattle of conveyor belts and pulleys and the hum of the air-conditioning.

The sheer volume of Priuses being built here speaks of its achievement. For two decades, no car has done more to alter the public perception of the hybrid automobile and to pave the way for electric vehicles. Black Priuses, thanks to Uber, have become ubiquitous on the streets of capital cities. They are verbal shorthand for generic, efficient, classless transportation. The Prius's job is, in many ways, complete. Toyota is now working on another vehicle - one that has the potential to change our relationship with cars all over again.

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Takeshi Uchiyamada, chairman of the Toyota Motor Corporation Christoffer Rudquist

Shoichi Kaneko is deputy chief engineer on the fourth-generation Prius, which launched in 2016. Slight, spiky haired and nervous, he explains the new model's genesis, his enthusiasm growing as he does so. "Generation-three Prius had a big role in getting hybrids known to the world. It sold very well, both in Japan and overseas," Kaneko says. "Our goal for developing the fourth generation was to create the de facto standard of what we wanted from a hybrid car without sacrificing other qualities."


The latest Prius also has the most radical look yet. "The first three generations had what we call a "happy face", Kaneko explains. "With the fourth generation, we tried to appeal to younger customers as well, so we changed the face to be more defiant."

Prius means "superior" in Latin. When the first generation arrived in the UK and US in 2000 it rapidly assumed cult status, earning celebrity endorsement from environmentally minded celebrities such as Leonardo DiCaprio, Cameron Diaz and Larry David. The Prius benefited from California's progressive attitude on ultra-low-emission vehicles and eventually became the state's best-selling car. In Japan, however, the Prius sold well, but became increasingly associated with an ageing customer base. Innovation was swiftly subsumed by tradition. Hybrids, it turns out, weren't sexy. Toyota has attempted to back out of this branding cul-de-sac by focusing on technology, with the introduction of a more advanced plug-in hybrid version (PHV) in 2012.

On paper, the present-day Prius falls short of its rivals. Tesla has wrestled away its credentials as the car of choice for the conspicuously eco-conscious. Its range falls short of true electric rivals from Nissan, General Motors and others. "We collected data from the first-generation car - Japanese motorists tend to only drive 20km a day," Kaneko says, in reference to the Prius PHV's electric-only range of 60km. Most PHV drivers used their cars as if they were fully electric, making short hops between charge points and rarely filling the tank.

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For the company that shaped a generation's attitude to petrol-powered cars, Toyota is reluctant to change too much too soon. "Toyota sees that gasoline fuel has many years to go. It's cheap and easy to deal with. [Internal-combustion-engine] vehicles will last for many years," Kaneko says. This innate caution goes hand-in-hand with Japan's susceptibility to extreme weather and natural disasters. "Our different regions have a varied climate. People can get stuck in their cars in the snow. Emergency services bring fuel to save them - electricity doesn't have that kind of portability. Fossil fuels allow cars to be used as shelter in certain situations."


Some of Tsutsumi's 1,850 robots await their next job Christoffer Rudquist

The origins of Toyota lie in the Toyoda Automatic Loom Works, founded in 1926. Car-making began in 1937, after a study of foreign models and methods. Today, Toyota is comprised of more than 12 sub-groups providing everything from steel components to air conditioners, forklift trucks and even houses.

The original Prius's development was fast and furious - very different from how the company had previously worked. The car's gestation is charted in Hideshi Itazaki's book The Prius that Shook the World, published in 1999. (The title is a nod to the 1990 bestseller The Machine That Changed the World, which introduced Toyota's lean-production concept.) Itazaki's book is written in the breathless style of the Japanese business novel, a hugely popular fiction genre that sidesteps Japan's traditionally deferential relationship between media and business by using corporate culture as a backdrop for action and romance. This telling of the Prius story does its best to bring drama to the banal. One passage reads: "Shimatani-kun, I feel rather awkward, but would you help us out in the mass-production division? We need the diagonal-beam technology that you developed."

The Prius was the result of Toyota's G21 project, which was established in September 1993 to design a car for the next century. The man in charge of G21 was engineer Takeshi Uchiyamada, now chairman of the entire Toyota Motor Corporation. Today, Uchiyamada is sitting in a brown-tinged boardroom high up in Toyota's Nagoya HQ, joined by a translator and two PR people. Immaculately turned out in a white shirt and navy pinstripe suit with a red pocket, the grey-haired 71-year-old executive has been Toyota's chairman since 2013. A company lifer, he began his career in 1969 in computing and research, exploring ways of reducing vibration. His father, Kameo Uchiyamada, was also a chief engineer at the company.

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"It was the first project that shared information over the internet. Collaboration between production engineers and design engineers was much stronger," Uchiyamada says. The environmental credentials weren't even part of the initial brief for a 21st-century car. Without a specific focus, the team brainstormed the desires for next-century transport; Uchiyamada claims credit for settling on an eco-friendly design.

Toyota's bosses had initially set the G21 group an ambitious fuel-economy target of 20.1kpl. Then, a year later, Uchimayada's new bosses decided to double it. (In the book, Uchimiyada calls the target outrageous.) A hybrid engine - long theorised, but never used in a mass-production vehicle - was the only option.

The Mirai's hydrogen tanks are fitter at Toyota's LFA works Christoffer Rudquist

"The most challenging thing was the battery development," Uchiyamada says. "Lithium-ion was not available. High-power nickel-cadmium didn't fulfil our performance requirements. We developed a nickel-hydride battery, but at the start its performance was only half of our requirements."

Eighty engineers worked for two years to develop a powertrain that would deliver on the seemingly impossible target. The divisions competed fiercely so as not to be the one delaying the project. "I received a lot of complaints that my manage-ment style was too rough," he recalls.

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The concept shown at the Tokyo Motor Show in October 1995 simply highlighted the system's limitations. It was named Toyota-EMS (Energy Management System) to hide the use of hybrid technology from rivals, and the design had many compromises. But the powertrain worked.

Uchiyamada wanted an open competition to design the Prius's body, but Toyota's management resisted the idea and an internal competition was held instead. The final design was by Irwin Liu at Calty, Toyota's Californian studio. The Prius MK 1 is prosaic in the extreme, but that didn't really matter: it was a car for motorists who care more about what cars mean, rather than how they look.

Uchiyamada says he immediately knew the Prius would be a success. "Sales started in December 1997, two months after we first showed the car. We had five times the volume of orders than planned. Sales and marketing thought we'd sell 300 cars a month. We sold 1,000."

Through the TPS - relentlessly focusing on hundreds of small improvements in the production process - subsequent models performed better. (It wasn't until the second iteration that the Prius took hold in the west.)

Today, Toyota's hybrid system is installed in around ten million of its cars and licensed to other manufacturers, including Nissan and Ford. Every major car manufacturer either provides or promises a hybrid alternative. The VW emissions scandal has shaken the automotive world. The year 2017 has been marked by manufacturers and governments disavowing the internal combustion engine and setting tough deadlines for its demise. Now, Toyota is betting on potentially far more significant technology - and hopes to disrupt the industry all over again.

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An unobstructed view of the hydrogen fuel cell engine, before the power control unit is installed Christoffer Rudquist

In January 2017, Toyota and 13 other companies including Honda, Hyundai, Daimler, Shell and Total announced the Hydrogen Council, a group focused on developing hydrogen as an alternative to fossil fuels. Although electric vehicles are becoming mainstream, many in the industry consider hydrogen to be the true successor to fossil fuels. Hydrogen is expensive and difficult to store, but it is clean. The chemical reaction in a fuel cell produces only water. It is also quick to refuel, unlike batteries. Japan has announced its intention to become the world's first hydrogen society. Toyota hopes that its new car, the Mirai, could end up being to hydrogen-fuel-cell vehicles what the Prius was to hybrids.

Mirai is a female Japanese name, meaning "future". With a range of around 650km and a low centre of gravity, the Mirai drives and handles like a regular car. Its only emissions are water. Like the Prius, it's friendly looking; aesthetically safe, if not groundbreaking. (Anthropomorphism plays an important role in Japanese car culture, as Karasawa alluded - cars aren't as much signifiers of status, but objects of endearment.) Japan-only models have a plug in the boot that can supply up to 60kWh of electricity from the battery - or around a week's supply for the average family of four.

Mirai chief engineer Yoshikazu Tanaka says that the saloon car's design aims to make fuel-cell vehicles mainstream. "To start the hydrogen society, we needed to sell an ordinary passenger car. So we developed the Mirai," he explains.

The Mirai is built at the LFA Works at Motomachi, near Nagoya. It is one of Toyota's most prestigious manufacturing centres, where workers are often sent by other factories to learn specific processes and become trainers and leaders. The Mirai line is similar to a supercar workshop, producing a maximum of 13 cars a day - 4,605 in total at the time of our visit (of which precisely 2,687 were built for export, mostly to California). Robots and heavy-lifting equipment are conspicuously absent, although the scanned and stacked supply system and jaunty-sounding andon boards are all present and correct. The main obstacle to speed, aside from the immature state of the hydrogen market itself, is the time and effort it takes to make the fuel-cell stack and hydrogen tanks. Tolerances are critical; hydrogen's volatility is greatly tempered by safe, pressurised storage and every set of twin tanks is tested with inert helium to ensure there are no leaks in the slim pipes feeding into the stack.

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The thick-walled hydrogen tanks are spun from carbon fibre-reinforced thermoplastic (CFRP), an impact-resistant structure that is not only tested during assembly, but which has been designed to shut down its valves in the event of any impact or damage. Workers use Bluetooth torque wrenches that beam data into a central computer. This ensures that every bolt is tightened the requisite amount during installation, while piping is kept outside of the passenger cell and a thicket of sensors detects any leaks. "It's improbable that the hydrogen would start a fire," plant manager Akifumi Karasawa says. He explains that US testers have to shoot tanks with firearms; the hydrogen evaporates through the bullet hole and rises to disperse in the atmosphere, rather than pooling at ground level the way petrol does.

Robot arms weld panels to create the Prius's body Christoffer Rudquist

There's a crucial difference between the Prius and the Mirai: the absence of hydrogen infrastructure. Hydrogen production, transportation and bulk storage are still major challenges. The vast majority of hydrogen is generated using fossil fuels, which simply shifts C02 generation from tailpipe to production facility. And what the combination of fuel cell and electric motor make up in efficiency, they lose in density; you need more space for hydrogen storage compared to regular petrol or diesel, issues that increase dramatically when you consider tankers, pipelines and on-site storage. Hydrogen's proponents acknowledge the enormous costs involved in creating even a modest network; its critics dismiss it for all but the most specialist applications.

Building the Mirai illustrates the complexities involved. It takes about four days for the raw metal and components to be bolted together into a single car, which is about twice the length of time of a regular saloon. Making 2,000 Mirais a month requires intensive automation. The car is being "productionised" so that it can shift away from its meticulous workshops and on to the regular lines.

A Prius with Thermo-Tect paint, which boosts solar reflectivity Christoffer Rudquist

It's here that the TPS will be tested. The engineering challenges facing the Mirai are greater than those faced by Uchimayada's team when developing the Prius's hybrid engine. But, if the world is to embrace fuel-cell cars, the odds are that they won't be built by a boutique startup; economies of scale require scale. If any company can make hydrogen cars popular, it'll be the one that did so with hybrids, 20 years ago.


Toyota's goal for the Mirai now is to increase production, starting with the second-generation model. The company plans to unveil it to the world at the 2020 Tokyo Olympics, alongside the Hino hydrogen bus being developed by the group and, if rumours are to be believed, a Toyota-developed "flying car".

"I want to do two things," Tanaka explains. "To establish the technology so we can make different vehicles. And to improve production capacity. To start the hydrogen society, we must extend capacity ten times more."

Jonathan Bell is editor at large at Wallpaper. He wrote about IKEA's secret design lab in issue 10.15