Key technical point is that the polar moment of inertia (concentration of mass around center) of a Tesla, to the extent of our knowledge, is better than any other production car. This positively affects safety, handling & driving feel. Extremely important metric.
A Detailed Look At How Tesla Makes Incredibly Safe Electric Cars
IN-DEPTH: HOW TESLA PRODUCES THE SAFEST CARS ON THE PLANET
*This article comes to us courtesy of EVANNEX (which also makes aftermarket Tesla accessories). Authored by Iqtidar Ali. The opinions expressed in these articles are not necessarily our own at InsideEVs.
Above: Tesla’s cars currently in production (Instagram: theelectriccar via Tesla)
Meanwhile, Tesla is redefining vehicle safety standards and they’ve achieved this audacious goal by bringing together industry-leading design, engineering and software.
Tesla’s electric vehicles not only achieved a 5-star rating in every category of NHTSA’s crash tests but Model 3, Model S and Model X are the top three cars with the lowest probability of injury to occupants that NHTSA has ever tested.
Above: Tesla Model 3 has the lowest probability of injury of any vehicle ever tested by NHTSA followed by Model S and X (Source: Tesla)
Looking at the graph above, Tesla happens to be the first and only manufacturer with an entire lineup of cars with superior safety ratings — 1st, 2nd and 3rd are all Teslas — and it’s likely that the upcoming Model Y will join the rest of her siblings to round out the company’s safety mission.
SAFETY ENGINEERING & DESIGN
Electric vehicles are generally safer than internal combustion engine (ICE) vehicles due to the fact that their ‘center of gravity’ is almost perfectly situated. However, Tesla takes this to a whole new level with the Model 3 design — in addition to a lower center of gravity, Model 3 has an extremely low ‘polar moment of inertia’, Tesla defines this in their press release as follows:
In addition to its near 50/50 weight distribution, Model 3 was also designed with an extremely low polar moment of inertia, which means that its heaviest components are located closer to the car’s center of gravity. Even though Model 3 has no engine, its performance is similar to what’s described as a “mid-engine car” due to its centered battery pack (the heaviest component of the car) and the fact that Model 3’s rear motor is placed slightly in front of the rear axle rather than behind it. Not only does this architecture add to the overall agility and handling of the car, it also improves the capability of stability control by minimizing rotational kinetic energy.
Tesla Model 3 Design: ~50/50 weight distribution with heaviest components near the low center of gravity delivering a ‘low polar moment of interia (infographic) – Click/Tap for high-res version — (Image: Tesla, Illustrated by: Iqtidar Ali)
Elon Musk further explained the ‘Polar Moment of Inertia’ in a series of tweets:
Above: Tesla Model S Crash Test (NHTSA)
During Tesla’s Q3 earnings call, Madan Gopal, Functional Lead and Principal Safety Engineer, was describing how Tesla Model 3’s architecture and design adheres to the highest safety standards and Elon Musk noted:
Yeah. I think, architecturally, we have Newton on our side. And having Isaac Newton on your side is definitely the way to go.
Tesla’s Q3 earnings call actually kicked off with the ‘Safety of Tesla Vehicles’ and Madan Gopal and Elon Musk went to great lengths to describe why ‘vehicle safety’ is the company’s top priority (listen to the earnings call webcast here).
CRASH SAFETY RATINGS TESTS
National Highway Traffic Safety Administration (NHTSA) has tested 943 vehicles since 2011 and taking into account ‘lowest probability of injury’, Tesla vehicles are the ‘top three’ — meanwhile the remainder (of the 940 vehicles) are from every other car manufacturer.
All of the vehicles achieving a 5-star rating are not the same as Madan Gopal described it on Tesla’s Q3 earnings call:
Yeah, exactly. So if you look at [that] there, there is a metric we came up with, which is a part of US NCAP rating itself, as a lowest probability of injury. And Model 3 has the lowest, and just to give you context, there are total of 900 plus vehicles since 2011, which have been rated. So the fact [is] that Model 3 is the best among all the 943 to be exact. So that speaks volumes. And I’m very happy to say what Model 3 has achieved.
Due to the absence of an internal combustion engine in the front of a Tesla, this frontal space serves as a large crumple zone that absorbs the impact and it not only provides added safety for vehicle occupants but also for pedestrians in an incident.
Tesla Model 3 Design: Large Front Crumple Zone – Click/Tap for high-res version — (Image: Tesla, Illustrated by: Iqtidar Ali)
Let’s compare the front collision tests of a Tesla Model 3 and an Audi A4 in the following video where Model 3’s large crumple zone absorbs most of the impact and Audi A4’s engine thrusts towards the passenger cabin.
Above: Tesla Model 3 vs Audi A4 front collision comparison video (Source: Tesla)
Even with a dual-motor setup a Tesla is engineered to pull the nose of the front motor downward and avoid intrusion into the passenger cabin (video below).
In Tesla’s own words:
In pole impact crashes, in which a narrow obstruction impacts the car between the main crash rails, energy-absorbing lateral and diagonal beam structures work to mitigate the impact. This includes a high-strength aluminum bumper beam, a sway bar placed low and forward in the front of the car, cross-members at the front of the steel subframe that are connected to the main crash rails, and additional diagonal beams in the subframe that distribute energy back to the crash rails when they aren’t directly impacted. An ultra-high strength martensitic steel beam is also attached to the top of the front suspension to further absorb crash energy from severe impacts, and the rear part of the subframe is shaped like a “U” and buckles down when impacted.
Above: Tesla Model 3 front collision with dual-motor setup (Source: Tesla)
Also the airbags used in Tesla vehicles are specially designed for maximum safety and work in combination with the sensors installed in both the driver and passenger seats in order to determine the size of the seat occupant and inflate only to the extent required — other manufacturers typically order airbags from a third party and just install them in their cars to fulfill basic safety requirements. As such, we’ve witnessed recent recalls due to injuries and deaths related to faulty airbags and airbag systems.
Above: A look at Tesla airbag deployment (Source: Tesla)
The Tesla Model S owner’s manual describes how Tesla’s specially designed front airbags function:
The front airbags on the Model S are advanced airbags designed to reduce airbag related injuries to children or small adults who ride in front. On the driver’s side, the front airbag works with a seat position sensor that adjusts the inflation level based on the size of the occupant. On the passenger’s side, the airbag responds to a sensing system in the seat that determines whether or not the passenger side front airbag inflates, and adjusts the inflation level based on the size of the occupant
Tesla’s vehicles exhibit exceptional safety in a side impact or intrusion incident as a rigid battery pack plays a pivotal role in stopping the colliding object from entering the cabin in a manner that’s too deep to be considered safe — this also makes the Tesla side airbags perform better than an ICE car — giving them more time and space to save the occupants.
Additionally the Tesla Model 3 design uses ultra high-strengh steel reinforcements in the door panels and roof structure for increased rigidity against a side collision (illustrated below).
Above: Tesla Model 3 architecture uses high strength steel reinforcements in door panels and roof structure (Images: Tesla)
The following comparison video of a side pole intrusion test between a Tesla Model 3 and a Lexus ES 350 shows us the difference in a side impact incident.
Above: Side pole intrusion test comparison between Tesla Model 3 and Lexus ES 350 (Source: Tesla/NHTSA) — all Model 3 NHTSA crash test videos here.
The low center of gravity in a Tesla vehicle reduces the risk of a rollover incident significantly. In addition, the overall design and structural rigidity of the vehicle reduces the risk of injury even if a Tesla car does rollover.
Tesla’s internal tests show that the Model 3 body structure can withstand roof-crush loads equivalent to more than four times its own weight and with minimal structural deformation.
*Model 3 Long Range Weight = 3,814 lbs (1,730 kgs) x 4 = 15,256 lbs (6,920 kgs) = more than an african adult male bush elephant (the largest living terrestrial animal)
The following rollover risk test of a Tesla Model X by NHTSA shows how difficult it is to rollover a Tesla.
Above: A Tesla Model X being tested for rollover safety (NHTSA/DPC Cars/YouTube).
SAFETY TECH / AUTOPILOT
Currently no other car manufacturer can claim that they can improve the safety of their vehicle fleet via an over-the-air (OTA) software update — this remains an area where Tesla maintains a unique edge over legacy automakers.
For example, earlier this year Consumer Reports tested a Tesla Model 3 and found that the braking distance was more than they would typically recommend — in turn, Elon Musk promised to improve the stopping distance via an OTA update and Tesla successfully reduced the stopping distance by nearly 20 feet by re-calibrating the ABS, hence Consumer Reports added Model 3 to their ‘CR Recommended’ list.
All Tesla vehicles manufactured after November 2016 have 12 ultrasonic sensors, 8 cameras and 1 forward radar that help provide Autopilot with 360° vision of its surroundings — this provides the most advanced, integrated sensor suite in any production vehicle today (see below infographic).
Above: HW 2.0+ Tesla Vehicles – 360° Autopilot Vision and Radars – Click/Tap for high-res version of the infographic (Source: Tesla)
Recently, European New Car Assessment Program (Euro NCAP) tested several vehicles for their Driver Assistance/Automated Driving to calculate safety measures. In turn, they selected a Tesla Model S for evaluation and it performed better than most cars from other manufacturers — however, an outstanding issue with Euro NCAP seems to be the name ‘Autopilot’ which they feel doesn’t sound like a driver assist system, rather a full self driving setup. Check out the Autopilot testing video below.
Above: Euro NCAP 2018 Automated Testing a Tesla Model S Autopilot
As mentioned previously, Tesla is consistently working to improve safety and Autopilot features with new updates, as Madan Gopal, the company’s Functional Lead and Principal Safety Engineer, had explained during the Q3 2018 Tesla earnings call:
We are not stopping right now. What we would like to do next is [show] how we can make use of the active safety and autopilot features, and make it even more [of an] improvement, so the next area that we are focusing on, how to integrate active and passive safety… that’s our next area of challenge, which we will improve for sure.
STANDARD SAFETY FEATURES
It’s worth noting that all Tesla vehicles come with a great set of safety features right out of the box even if you don’t opt-in for Enhanced Autopilot (EAP) at the time of your Tesla purchase. Following is a list of safety features that come standard on any Tesla vehicle.
active safety technologies including collision avoidance and automatic emergency braking
Written by: Iqtidar Ali (@IqtidarAlii/Twitter) – DM open for tips and feedback.
*Editor’s Note: EVANNEX, which also sells aftermarket gear for Teslas, has kindly allowed us to share some of its content with our readers, free of charge. Our thanks go out to EVANNEX. Check out the site here.