Bus Features, Safety, Technology

Yutong YESS system raises the bar for electric bus safety

Since Yutong’s YESS safety system was first included in Australian buses in 2020, Yutong has investigated ways of improving electric battery safety that goes above and beyond global standards.

There’s no hiding that a major barrier to the initial uptake of electric buses and coaches around the world was the safety side.

With so many new elements being part of a zero-emissions bus compared to diesel technology, the first battery electric buses were met with hesitancy.

As electric vehicles continue to steadily sweep over the transport industry, large global manufacturers have made headway on safety changes. Yutong is one of these leading the way. Its latest YESS (Yutong Electric Safety Standard) safety system, which is now onboard all electric Yutong buses distributed by VDI Australia, makes these buses and coaches safer than ever before.

“The YESS system has been in our buses for 18 months now,” VDI Australia Product, ZEB & New Technologies Manager Luke Edwards told ABC. “Overseas there were issues with electric vehicles when it came to collisions.

“To increase the safety for customers and passengers, we identified the major factors involved in vehicle impacts and introduced a safety barrier for our batteries.”

Edwards says protecting electric batteries is the first priority when it comes to safety. By keeping batteries safe, thermal events and passenger dangers can be averted in the event of a vehicle collision.

This safety barrier comes in the form of the YESS safety system. VDI Australia distributed the first vehicles to include the revolutionary battery electric bus system after production began in 2020. Vehicles subsequently delivered in Queensland were the first to include the system that also improves the safety of battery packs.

The YESS safety system starts by reinforcing the areas of the bus that surround where the batteries sit. This stronger material means batteries are much less likely to receive any damage when a collision occurs.


“We started by introducing a safety barrier to our batteries, especially when they’re located low in vehicles and need additional structures to ensure the batteries are harder to damage in a collision,” Edwards says. “Prior to the YESS safety system, you could get a car travelling at 50 kilometres per hour to hit the vehicle and the batteries would be damaged. Now, we have tested an 18 tonne truck hitting the bus at 50 kilometres per hour and there’s no damage to the batteries.”

After this initial addition to Yutong buses, the global brand ventured into increasing its thermal protection.

“Yutong then looked into making the thermal management of the batteries a liquid based system as a second part to the YESS system that was a major step forward in safety,” Edwards says.

After Yutong’s factories improved the structure surrounding the battery, they identified that the electric heating part of thermal management should be removed to keep the battery pack as safe as possible.

From 2021 onwards, Edwards says the improved YESS system relies on a process where liquid is heated to warm the batteries and cooled down to drop the battery’s temperature, depending on the climate and what the battery requires to remain efficient and safe.

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In previous global incidents of electric battery fires, the heating system of a battery system would stick and overheat. Yutong identified that if it took the thermal heating aspect out of the battery then it’s easier to protect against thermal runaway.

“Our next step after this was to inject nitrogen into every battery pack, which was a truly groundbreaking move inspired by the aviation industry,” Edwards says. “Nitrogen is an inert gas, so if a cell has a thermal runaway issue then it is much harder for it to travel to the next cell within the battery.

“The nitrogen stops the battery from being able to start its own fire and then spread it. As a result of further research and development, Yutong proceeded to install our battery packs so that they have a membrane on top of the battery cell that provides a case that is designed to cater for a fire burning in the battery for two hours at 1300 degrees Celsius before the system and battery can’t contain it within the pack.”

If this thermal protection wasn’t enough, Edwards says Yutong went the extra mile with its YESS system. To complement these precautions, the global bus and coach brand then added an additional fire blanket on top of the battery packs to create a total system that dramatically reduces the chances of an electric bus battery fire.

This four-pronged approach, starting with the collision impact reinforcement and ending with the outer fire blanket, looks at every aspect of the electric bus battery. Edwards says Yutong’s research and development team put in an immense amount of effort to gradually improve safety systems onboard its electric buses and it isn’t done yet with the innovations.

“The amount of research and development that goes into our products accounts for around five per cent of Yutong’s annual turnover,” Edwards says. “I now see the Yutong electric vehicles as being the safest electric buses in the market.

“Yutong is stringent on its temperatures and how it measures them. Our telematics systems run 24/7, not just while the vehicle is on, so Yutong and the operator will be notified in real time if any of the battery cells are outside of the set parameters. The YESS system will continued to be improved upon to provide even higher levels of safety in the future.” 

All of these factors make for an electric bus safety system that covers all facets. The YESS system has received global credit from the likes of global bus and coach event organiser BusWorld. Edwards is proud to say that the revolutionary system first proved its abilities in the Australian climate.

He now wants all members of the local bus and coach industry to follow Yutong and VDI Australia’s lead when it comes to lifting the bar with electric bus safety.

“Yutong prides itself on having one of the safest buses in the market,” Edwards says.  “We want to keep our systems at the highest level of safety possible and push this through to other manufacturers around Australia.

“We know that some vehicles are well behind. What we’d love to see most at VDI Australia is a level of safety in all electric buses and coaches that is similar to our YESS system so that passenger and operator confidence in electric buses isn’t tarnished by a thermal incident.”

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