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EV fires on Cook Strait ferries: Ministerial expert panel to examine safety

In brief
  • Fire safety for EVs on Cook Strait ferries prioritised by new advisory panel after a $3 billion upgrade plan cancellation.
  • EV fires pose higher risks than ICE fires, challenging to control and extinguish.
  • Cook Strait’s harsh conditions and lack of rescue support complicates fire management on ferries.
  • International warnings highlight the danger.

EV fires less common, but far more dangerous

Fire safety on the Cook Strait ferries carrying increasing numbers of electric vehicles is expected to be a top priority for the new expert advisory panel appointed after the government torpedoed a near $3 billion upgrade plan before Christmas.

While topline data is often quoted to suggest Internal Combustion Engines (ICE) are five times more likely to catch fire overall than EV’s, it is strongly suspected that EV’s are much more likely to burst into flames spontaneously while switched off, making them an unpredictable risk in garages, parking lots and onboard ferries.

But that’s not the whole story either. ICE fires are easy to contain and extinguish, with an average car fire needing less than a thousand litres of water. EV fires, in contrast, can soak up more than 44,000 litres (44 tonnes) and still be burning hours or even days later. Their combustion temperature is high enough to melt the decks of a ship.

When the lack of any ocean tugboat rescue capability in Cook Strait is factored in, along with notoriously rough seas making conditions for onboard fire crews and aerial evacuation of passengers difficult, the potential for tragedy is high and will only escalate as more EV’s join the vehicle fleet.

Scandinavian research reveals the unpredictability of EV fires on ferry car decks

Danish fire researchers simulated a ferry car deck fire with one EV parked amid eight ICE vehicles, and found the results unpredictable: “We experienced great variations in the development of the fire, even though we had the same setup for each test. In our fourth test, for example, the fire had already spread to the other cars after two minutes,” the research director noted. 

He also revealed that it takes ferry crews 10 minutes on average to respond to alarms from a car deck fire. Potentially a ship can be well ablaze long before fire crews are on the scene.

Here in NZ, Kiwirail insists it has the capability to fight an onboard EV fire, as Autocar NZ reported two years ago: “Specialist firefighter equipment is fixed on all three Interislander ferries. Drencher systems, CO2 smothering systems, fixed water cannons, and water curtains will maintain an EV fire. Ferries and terminals have fire blankets specifically designed for EV fires.”

However, all those things require instant, automatic deployment in the right area at the right time, and there’s no guarantee they’ll work. Overconfidence in tackling EV fires has sunk several vessels boasting similar equipment. 

In 2023, big Norwegian ferry operator Havila banned EV’s from its ships on the grounds that EV fires, whilst rare, were not realistically possible to contain on a ship.

 EV fires prevention and safety measures - Crucial fire safety protocols for EVs
The Fremantle Highway suffered serious damage possibly due to an EV fire onboard in mid 2023. Image: Uberprutser

Australia’s Maritime Safety Agency has just warned that EV fires should not be directly tackled by fire crews because of the high toxicity of the gasses emitted and the potential of those gasses to explode in enclosed spaces.

No response from the NZ government yet

A spokeswoman for NZ Transport Minister Simeon Brown says he has not been briefed on the dangers of carrying EV’s across Cook Strait, and whether that has been properly planned for. A subsequent news release listed safety as the first priority for the new advisory panel. 

The establishment of the group also recognises that the Crown has interests that may be wider than KiwiRail’s commercial interests,” Nicola Willis says.

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