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MC Explains | Why six airbags may not be enough

Airbags are not the most critical component of safety in a car crash. Must we place such a premium on them and overlook a key aspect of automotive safety?

July 03, 2022 / 10:56 AM IST
Representative Image

Representative Image

The effectiveness of airbags has come under scrutiny again after the Kia Carens, famous for being equipped with six airbags as standard, received a three-star safety rating from Global NCAP in a crash test.

The Carens scored low on the structural integrity of the shell while providing less-than-ideal protection to the feet and chest of the driver. In contrast, the Mahindra XUV700 received a five-star rating, partially due to the integrity of its monocoque shell. 

The report comes months ahead of the six mandatory airbag rule taking effect in October.

First line of defence

Shortly after the Carens test concluded its SaferCarsForIndia campaign, Global NCAP carried out another test using a US-spec Hyundai Accent (the cheapest of the cars sold by the South Korean giant in the US) and an India-spec Hyundai i10 Aura sold in Mexico.

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The Hyundai Accent, equipped with six airbags and electronic stability control (ESC) as standard, came out on top and the i10, fitted with only dual front airbags, received what would be a 0- star rating by Latin NCAP. 

The outcome had more to do with the fact that the Accent showed greater structural integrity and the i10 didn’t. Airbags seemed incidental. The report said it was poor structural integrity that doomed the i10. 

“The protection the Accent offered to its driver during the crash test was good and the model showed a stable structure. The Grand i10 however showed an unstable structure and poor protection to the driver with a high probability of life-threatening injuries,” it said.

While the Car2Car test was carried out to highlight the safety double standards for developed markets against the developing ones—something which Korean carmakers seem particularly guilty of—it did emphasis the importance of structural safety as opposed to electronic aids and multiple airbags. 

A recently approved Bharat NCAP draft proposal says that all cars sold in India should be equipped with six airbags, ESC, a three-point safety belt for the middle seat passenger in the second row and pedestrian protection as mandatory features. The proposal, however, doesn’t talk about the shell structure—arguably the most important safety component in the event of a crash. 

Life and death question

So, just how important is structural strength as compared to airbags? According to Mahindra’s Chief Design Officer Pratap Bose, it’s a joint effort, but it’s the structure that can make the difference between life and death. 

MC explains logo

“I think both work hand-in-hand—the structure and the airbag system but the structure is fundamental. If you don’t get that right, you can have any number of airbags and you won’t survive a crash of high speed. The structure distributes the load in a certain way” says Bose, who's car designs, for the most part, have ranked high on all safety parameters. 

“It’s the first defence system. The structure has to hold so that you can open the doors after a crash, which I think is a crucial requirement. If people are trapped inside and you can’t get to them because the structure has collapsed, then the airbags don’t help”, says Bose. “This is why we call airbags the supplementary restraint system. It supplements the primary safety system which is the outer structure.”

Steel yourself

Most brands, including Mahindra, boast of using lightweight yet increasingly high-tensile, high-strength steel for their chassis. Why do some fair better in Global NCAP tests?

According to R Velusamy, the senior vice president and head of product development at Mahindra, “When it comes to receiving a 5-star safety rating, you need high-strength steel. It doesn’t matter as much when you’re dealing with a two or a three star-rating but for optimum safety, you need high-strength, high-tensile steel”. 

What is the cost difference between the steel used for cars that, according to Global NCAP, have a high rating on structural integrity and brands that don’t? Is the difference significant? 

“No. The cost is in the restraint systems. If you design the structure well enough, the cost difference isn’t much. Certainly not for a car of Rs 18 lakh,” Velusamy says, pointing to the newly launched Mahindra ScorpioN. 

Can a six-airbag rule make a huge difference, especially in cars that do not cost as much and make up for the majority of India’s automotive purchases? 

“You have to have the structure right,” says Velusamy, the foremost engineering authority at Mahindra & Mahindra. “The airbag is just a cushion, no matter where it’s placed”. 

“If you imagine a high-speed crash that is taking place, it’s all done in milliseconds. You crash it and roundabout in 40 milliseconds you reach a G-value of 34Gs. And, then you start coming down. So, it’s the frame that absorbs the crash then it hits the tyre and the tyre hits the bottom of the engine. And that’s how the load transfer takes place” he adds, painting an accurate picture that isn’t always taken into consideration while buying a car. 

“You have to define the flow of energy absorbed. It all depends on the architecture.” 

Light is strong

Does the volume of steel used make a difference? No, says Shashank Srivastava, the executive director of sales & marketing at Maruti Suzuki. “There is a general misunderstanding that lighter steel isn’t as strong. In fact, today, when material technology is such that high tensile steel is lighter but much stronger,” Srivastava said.

So, what does Global NCAP’s ratings say about vehicle structural safety? 

“Global NCAP’s campaign is to make cars safer. That doesn’t mean the cars aren’t safe”, says Srivastava after the launch of the all-new Brezza, which boasts of a multitude of safety features, and has in the past, received a 4-star rating from GlobalNCAP. 

“Another misconception has to do with the crumple zone,” says Srivastava.“Whenever people see a car’s front crumple after a crash test, they think it’s structurally poor and so has collapsed. But in reality, crumple zones are important in order to not transfer the energy of the impact to the occupants inside. Crumpling isn’t a sign of a less safe car”. 

The Global NCAP website had a statement in January 2014 that said the Alto 800, Tata Nano and Hyundai i10 had received zero stars because “the vehicle structure proved inadequate and collapsed to varying degrees”. “The extent of the structural weaknesses in these models were such that fitting airbags would not be effective in reducing the risk of serious injury,” it went on to say. 

Indian carmakers have come a long way since 2014, adding a variety of safety features in the form of optional electronic aids along with dual airbags and ABS as standard. 

With the inclusion of ESC and a three-point safety belt for all passengers, the safety quotient is only going to go up. But the draft does intend to conduct crashes at a speed of 64kph in line with global standards instead of the previous 54kph. It would mean a harsher verdict on structural safety, leading, hopefully, to greater attention to the structural integrity instead of just multiple airbags and passive safety features. 
Parth Charan is a Mumbai-based writer who’s written extensively on cars for over seven years.
first published: Jul 3, 2022 10:56 am
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