There will be accidents
As robotaxi companies in the USA prepare to launch their autonomous vehicles in more cities, safety is in the spotlight again. And quite rightly.
Many autonomous mobility service companies have relied on two factors when developing their vehicles: active safety systems which help the vehicle avoid or mitigate the extent of a crash, and a maximum vehicle speed limit, which will reduce the extent of injuries to the occupants.
But the fact is that these vehicles are going to be out in mixed-mode traffic situations. There will be accidents – however much we all attempt to do everything possible to avoid them. When we developed the Steel E-Motive (SEM) body structure concepts for fully autonomous ride-sharing electric vehicles, we agreed on two basic principles – that these vehicles would operate at high speeds (top speed of 130 kph) in mixed mode traffic conditions, and that we, therefore, needed to engineer passive safety structures that met global high-speed crash requirements to protect occupants and the battery system in these use-case conditions. In this process, we discovered that no other provider of autonomous ride-sharing electric vehicles had fully shared details of passive safety structures engineered to those same high-speed crash standards.
Fortunately, our vehicle design process benefitted from a massive portfolio of modern advanced high-strength steels (AHSS) available through member companies of WorldAutoSteel. Steel E-Motive (SEM) was developed to show how AHSS can enable sustainable, comfortable, economical and safe ride-sharing vehicles by 2030.
The result is the first “robotaxi” to fully detail and report compliance to global high-speed safety standards. In developing Steel E-Motive, we targeted conformity with seven US crash standards, including US NCAP (New Car Assessment Program) IIHS and FMVSS (Federal Motor Vehicle Safety Standards) front, side and rear impact tests while also assessing performance against worldwide protocols, including NHTSA (US) Euro NCAP (European) and China’s GB 38031 standard for battery protection.
As an example, Steel E-Motive achieves the highest IIHS rating of ‘good’, this is particularly important as IIHS (the US-based Insurance Institute for Highway Safety), is highly regarded in its dedication to reducing deaths injuries and property damage from motor vehicle crashes.
Most production vehicles use new generation, advanced high-strength steels and technologies. We had no fewer than 64 AHSS materials to select from, enabling us to choose exactly the right steel for every need and purpose in the vehicle, including safety protection. These make a car stronger and more fuel efficient, as well as safer.
Nearly all vehicles on the road today are made of steel because it has the broadest range of properties while being the most affordable structural material for designing safe vehicles. Steel has a unique capacity to absorb an impact, and therefore to diffuse crash energy. It also becomes harder when it’s crushed, which means it will become stronger on impact, retarding further penetration into the vehicle’s passenger zone.
Here is an outline of how we designed steel’s benefits into the Steel E-Motive (SEM) concept when considering front and side crashes.
SEM features a high strength front protection zone, which reacts to the crush loads and minimises intrusion for the occupants in front crashes. The crush zones have been engineered to decelerate the vehicle progressively. The longitudinal mid rails, featuring tailor welded blanks fabricated with Dual Phase steels, are tuned to give a lower deceleration pulse into the passenger cabin to minimize injury threat. The side crush rails are designed to minimise intrusion into the cabin for occupant protection. Finally, a novel design geometry and Press Hardened Steels enable the new glance beam architecture to force the vehicle off of the Small Offset barrier; the resulting “glance-off” achieves significantly reduced crash energy and pulse into the passenger cabin.
When considering side crashes, we engineered the body structure for the IIHS 60kph deformable barrier test and 30kph side pole test, assessing both occupant and battery protection – and once again achieving the IIHS ‘good’ performance rating. Our side structures are comprised of a large one-piece tailor-welded door ring fabricated with press hardened steels, the TRIP steel B pillar housed in the side scissor doors, and a roll-formed hexagon rocker beam fabricated with Dual Phase steel.
These attain a very safe design, giving good levels of protection for both the occupants and battery modules exceeding 30mm intrusion clearance at critical measurement points.
SEM was also engineered for rear crash and roof crush, and once again the robust steel-intensive architecture exceeds crash standard requirements.
Electric-powered vehicle sales are accelerating, reflecting industry investment, and will soon achieve market domination from the combustion engine. In megacities, where congestion, pollution and exorbitant vehicle ownership costs reign, autonomous cars will replace drivers, and ride-sharing will become the norm. As we look into the future and recognize the need for these vehicles to offer comfortable, safe, affordable and sustainable transportation, we will still be designing them by harnessing the unique properties of steel.
The AHSS Extended Passenger Protection Zone provides excellent cabin intrusion protection and ultimately lower risk of injury. Press hardened steel (PHS) provides formability for challenging geometries, while Martensitic steel (MS) provides the strength to limit intrusion.
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