Could fewer crashes lead to lighter cars?

Autonomous vehicles may mean no more crashes, but passive safety is non-negotiable for future vehicle design. Freddie Holmes speaks to SSAB to find out why

Human error is linked to the vast majority of road collisions – 94% according to US safety regulator NHTSA – and this has driven the industry’s push for autonomous driving. Take away the potential for distraction, drowsiness, inebriation and the myriad other factors associated with human driving, and crashes should decline.

This could mark a significant step change for an industry that, for the better part of a century, has been developing stronger, more impact resistant vehicles. Is such a focus on crash safety still necessary for fleets of low-speed autonomous vehicles operating within geo-fenced areas, such as dedicated city streets or corporate campuses? Instead, super-strength metals could be cut out and replaced with significantly thinner, lighter materials.

In theory, the appeal is clear: that extra weight loss could facilitate significant jumps in electric driving range, more compact vehicle bodies that take up less space, and even the opportunity to house digital screens within body panels.

Is this just fantasy?

It is not the first time the subject has been brought into question. Bill Russo, an ex-Vice President at Chrysler and current Chief Executive of business advisory firm Automobility, suggests that automakers may no longer need to meet the crash requirements of a high speed Autobahn collision when designing cars for autonomous urban travel. “For urban mobility, cars are over-engineered,” he remarked at an event in Shanghai.

Holly Lei, a Senior Vice President at lightweight materials supplier Covestro, agrees. “Having just one autonomous vehicle on the road is not sufficient in order to transition away from today’s high strength materials,” she said. “But if every vehicle is autonomous, then it will not be necessary for body parts to have as much strength.”

For urban mobility, cars are over-engineered

For materials suppliers, it is indeed an interesting proposition, and none more so than for global steel producers that have dominated vehicle bodies for decades. As it stands however, cars are still driven manually, and passive safety tests are not getting any less stringent. Olof Carré, Head of Product Management for Docol products at SSAB, is confident that steel will retain the lion’s share of materials used in light vehicles for the foreseeable future. As he puts it: “The overall feeling today is that passive safety remains extremely important. The best solution for that is steel, and it’s been that way for many decades.”

That said, SSAB is considering the long-term implications of autonomous developments. In June 2018, the steel producer demoed a lightweight steel frame developed for an urban autonomous vehicle made by Finnish start-up Sensible 4. Grades of Docol Steel – SSAB’s automotive advanced high-strength steel (AHSS) – helped the vehicle’s frame to meet weight constraints without impacting strength.

Carré likens the potential ‘robo-cab’ experience of the future to that of a train ride: “You can just sit and eat your lunch, and take it easy,” he says. This will influence how vehicle structures are designed in future. “You want more open space in the car, so it will be interesting from a steel point of view; the car may have longer sections of ultra high-strength steel to allow the car to be more like a living room or office,” he suggests. “We will continue using super high-strength steel in order to reduce dimensions and make the structure lighter.”

Risky business

That said, it is still very early days for autonomous driving; Waymo only recently received a license from the California DoT to operate driverless taxis in the state, and for now, these will only be available to employees. Volkswagen has announced plans to fully commercialise a fleet of Level 4 autonomous taxis in Tel Aviv, Israel by 2022, while US start-up nuTonomy has trialled a similar service in Singapore for a few years now. Ford is working with Baidu to the same end in China.

While the outlook for autonomous driving has moved firmly into ‘when’ not ‘if’ territory, manually driven vehicles will rule the roost for years and decades to come. Most within the industry believe it would be naïve to assume otherwise, and that means efforts in crash structures must continue. “I’m not so sure that the requirements of passive safety will fall very quickly at all,” assured Carré. “There are still risks with autonomous driving vehicles, especially when combined with cars of today. Most people will still be driving themselves, and they could be drunk, tired or distracted and crash into you.”

The overall feeling today is that passive safety remains extremely important. The best solution for that is steel

It is also worth highlighting the mid-ground of autonomous vehicles in which drivers are expected to monitor semi-autonomous systems such as Tesla’s Autopilot, Volvo’s Pilot Assist and Cadillac’s Super Cruise. Autopilot in particular has come under significant scrutiny thanks to a spate of crashes in recent years, some of which have proved fatal.

It is not only the element of human error that comes into the equation, but also software malfunction. If the self-driving computer fails, a collision could be unavoidable and the consequences severe. This error could occur naturally, or as the result of a malicious cyber attack – both instances require that the vehicle retains a crash resistant structure. “There is a risk that the computer may break down, or somebody may hack into the car and take control of it. Because of this, automotive manufacturers will continue to develop passive safety for a long time,” explained Carré.

Don’t cut out steel just yet

Virtually all autonomous test vehicles require backup drivers to take control in an emergency, providing a final layer of safety. In a similar way, passive safety structures act as the fallback scenario in the event that a fully driverless car is unable to avoid a collision.

The ultimate goal is to achieve an entirely crash-free society, which is being pursued on an international level via the Vision Zero initiative. In the meantime, serious crashes will still take place and the body structure of vehicles must continue to be designed to reflect that.

Whether the material of choice is steel, aluminium or more exotic fibre-based structures, it is ultimately down to passive safety to keep occupants safe, regardless of the technology on board. World Auto Steel, the automotive group of the World Steel Association, has voiced a similar view. “It will take many years before all vehicles on the road have these technologies in play,” the organisation stated earlier in 2018. “Consequently, until every form of transport on the road is autonomous and connected, the need for passive safety will remain for the foreseeable future.”

This article appeared in the Q1 2019 issue of M:bility | Magazine. Follow this link to download the full issue.

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