Volvo bus safety builds on the belt

Date: 25.07.2023

Volvo’s history is steeped in pioneering safety technology. From theseat belt to the complex HVIL loop, Volvo Bus is pushing the boundaries of safety capabilities on its bus fleet

For Volvo Bus Australia, safety has always been paramount. As one of its three enduring core values, it has always placed premium value on giving its buses and coaches safety that goes above and beyond standards and expectations.

But what high-quality safety means hasn’t necessarily stayed the same. Back in 1959, Volvo was ahead of the game when its engineer Nils Bohlin developed an exciting piece of new heavy vehicle safety technology: the modern three-point seat belt.

In a defining moment that demonstrates Volvo’s attitude to industry-wide safety improvements, Volvo decided to leave the patent for the design open, making it available for all vehicle manufacturers to use.

More than a half-century later, Volvo Bus Australia’s suite of safety products look a fair bit different compared to the modern three-point seatbelt. While the seat belt has gone on to be credited with saving more than one million lives and is widely considered among the most cost-effective public health interventions, Volvo hasn’t stopped at this design when it comes to safety.

Its latest developments include adaptive cruise control, driver alert systems, dynamic steering and collision warnings. With the industry turning towards electromobility, Volvo is proudly leading the charge of what safety in electric buses should look like.

RELATED ARTICLE: Volvo supports local in new electric bus spree

For Volvo Bus Australia general manager Mitch Peden, safety is, and always will be, in Volvo’s DNA.

"While of course we need to extend our thinking around safety for battery electric buses, safety has always been at the core of what we do at Volvo," Peden told ABC.

"This focus on safety systems, of exceeding safety regulations, isn’t new. Introducing technology and backing up the systems with training for operators just makes sense to us, with safety at the core of everything we do."

Volvo Bus Australia head of Product and Engineering Mark Fryer says the safety innovations from Volvo on its buses and coaches, whether it be its diesel, hybrid or electric variants, include a wider range than ever before.

"Safety is one of our core values at Volvo and that has never gone away," Fryer told ABC.

"Alongside all of our safety products that monitor and ensure everything in our vehicles stay safe, our HVIL loop is at the forefront."

While Volvo’s safety suite is now large enough to fill a book, Volvo’s High-Voltage Isolation Loop (HVIL) design would grace the front cover nowadays. The idea behind the HVIL loop is to provide resistance monitoring and multi-layer cable protection at a speed and reliability seldom seen before.

While it’s not new on Volvo’s latest electric bus line – it’s been on Volvo’s hybrids for many years – it encompasses leading vehicle safety and electrical technology in its current format. Fryer says the HVIL loop starts when consumers are plugged into Volvo’s junction boxes.

"We have a traction voltage monitoring unit that surveys how much energy is required by the driveline and in turn how much energy will be put back into the ESS system through regenerative braking," he says.

"When everything is plugged into the 600V system, including all batteries for the bus and its consumers, it all utilises our HVIL loop technology that monitors all 600V components and the wiring harness."

This technology helps protect a wide range of features, including the bus’s batteries, air-conditioning and heating units and driveline technology.

The HVIL technology runs by ensuring that all 600V cables are connected securely at all times, allowing for a loop of power to keep everything running. Once connected, the bus can then provide a resistance reading on the Volvo wires.

By supplying its own wires and conducting plenty of testing, Volvo has finetuned the exact resistance reading it should have at all times. If the wires don’t have this reading, the power gets cut instantly, shutting down the bus quicker than the click of a finger.

"If the steel wire armour around these cables are compromised for any reason, the power shuts down. The HVIL loop goes through every single part of our buses that accept high voltage to create one big loop," Fryer says.

To put it simply, all of these measures and intricate wire designs dramatically decrease the risk of arcing and electric shock hazards, shutting down high voltage systems in the blink of an eye in the event of a cable or component being impacted.

Yet it’s not just electric safety that Volvo is focusing its expansive safety capabilities on.

The safety risk of battery electric buses is the thermal danger that the batteries pose. Although these thermal incidents may be highly unlikely, Volvo has implemented systems that are above and beyond the Australian standards for fire mitigation.

Instead of traditional diesel bus safety that centres on putting out fires before they can threaten the bus’s integrity and people onboard, electric bus safety is more about extending the time passengers and drivers have to safely evacuate the bus.

Unlike diesel bus fires, the event of an electric battery fire is far more intimidating. As part of its commitment to safety knowledge, Volvo participates in training with local fire brigades to mitigate the risk of electric bus fires.

To combat this dramatic fire risk, Australian regulations require electric buses to provide safety for between three and five minutes to evacuate everyone onboard. Volvo, as is its way, aimed to extend this time.

Through a range of factors, including self-extinguishing cells, thermal-protected floors and extra barriers on the outside of the bus, Volvo Bus Australia succeeded.

Fryer says a key part of this improvement was Volvo Bus Australia’s famous safety layer. For the Volvo fraternity, it’s known as ‘The Onion’, as the analogy of ‘onions have layers’ has been implemented into its cell designs within its electric batteries.

"The nine safety layers rule means that anything to do with high power must include nine rules of engagement or standards that it passes before Volvo begins its manufacturing process," Fryer says.

"To this point, Volvo has nine safety layers in its battery cells, ranging from chemistry choice and pack design to cell chemistry and short-circuit protection."

Outside of this innovative design, Volvo has looked at bolstering all parts of its buses to prevent the likelihood of a thermal event.

In the rear and back corners of the bus, Volvo added an extra 710mm of additional barrier that protects high voltage modules being impacted if the bus happens to be involved in a collision.

It then added thermal protection to its flooring and went through an investigation that determined that placing the batteries on the roof of the vehicle meant they were in the safest place away from hazards.

It’s a comprehensive approach to protecting the bus in a way never seen before. Fryer says this technology is only the tip of the iceberg, with Volvo Bus Australia’s safety suite onboard a bus being vaster than it ever has in Volvo history.

For a company dedicated to safety that its own engineer invented the modern seat belt, Peden concedes this is no mean feat.

"These accomplishments mean we’re extremely confident that our safety systems don’t just satisfy operator and legal requirements, but go above and beyond them," Peden says.

"Our goal has been to ensure our buses capture safety threats before they even arrive to make the vehicles as safe as it can be for all onboard.

"We know that our safety systems are complex and unique in Australia. We’ll continue to push the limits on safety technology to go beyond what has been accomplished before."

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