How Electric Vehicles Improve Fleet Safety

 In EV Industry

A fleet manager’s most important duty is ensuring the safety of drivers, passengers, and the public. It’s a matter of ethics, corporate citizenship, and good business. But with fuel (and electricity) prices low and premiums rising, insurance-related expenses are accounting for an increasing portion of per-mile operating costs for many fleets.

The average financial loss resulting from a vehicle accident is nearly twice as high as the average workplace accident, and according to the Bureau of Labor Statistics, roughly 40 percent of annual workplace fatalities involve vehicles.

Naturally, if the safety ramifications of a new technology or business practice are unproven, a good fleet manager won’t give it serious consideration.

Modern plug-in electric vehicles have only been on North American roads for about five years now. While they are all but certain to command an increasingly significant portion of new car sales in the coming years, their early success has been limited to key markets where public planning and government regulations are most favorable.

For many, the ins and outs of EVs are unfamiliar. How far do they go? How do they charge? For this article, we take a look at an equally important question: are electric vehicles safe?

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P.S. we put out an accompanying post on how to maximize the safety of your fleet’s electric vehicles, focusing on choosing the safest vehicles, encouraging safe driver behavior, and charging station deployment. You can read that article here.

Plenty of Smoke, Few Fires

In 2011, less than a year after the Nissan LEAF and Chevy Volt started their North American rollouts, a series of vehicle fires combined with political controversy over federal support for plug-ins created a misleading and unfair narrative about EVs: that they’re prone to catch fire without warning or provocation. First, a Chevy Volt caught fire nearly a month after completing a National Highway Traffic Safety Administration crash test. The NHTSA concluded that the fire wasn’t the result of a defect in the Volt’s design and issued a statement to the public that such events don’t constitute an increased risk of fire compared to conventional vehicles.

In 2012, Fisker Automotive—a small, high-end performance carmaker that went out of business but has since come back as Karma Automotive—experienced a string of unfortunate vehicle fires. Nobody was hurt in any of the incidents, and only one seems to have been the fault of the car itself.

One year later, the smashing success of the Tesla Model S was briefly derailed when a passerby posted video of the electric luxury sedan parked on the side of a Washington highway engulfed in flames. It would later be learned that the undercarriage of the vehicle had been pierced by a large piece of metal debris that had fallen off a truck, and that the Model S had warned its driver about the damage in plenty of time to pull over and exit the vehicle.

Tesla Fire

A roadside Tesla Model S fire helped stoke a mini-hysteria over the safety of EV batteries.

Understanding the Real Risk of Electric Vehicle Battery Fires

Lithium ion battery packs are the energy storage technology of choice for nearly every modern portable electronic device. Though designs and chemistries differ depending on the product and who makes its battery, one thing all lithium ion cells have in common is the potential for something called thermal runaway.

Like all metals, lithium has a melting point. If the temperature of a cell hits that melting point, it can cause the battery to destabilize and rapidly discharge stored energy at extremely high temperatures, creating fires or even violent explosions. This phenomenon is most widely associated with laptops, smartphones, and other small electronics, but it can affect any battery—not just those with lithium ion chemistry.

The good news is that there are a number of technology and engineering solutions that can reduce the level of danger from lithium ion thermal runaway incidents in cars and trucks to well below that of internal combustion vehicles.

  • Advanced battery management systems monitor the activity of each cell and relay information to a CPU, which can adjust the cooling system, warn the driver, and even shut down the battery entirely as soon as a problem is detected.
  • Carmakers also armor the battery packs of their vehicles to resist damage during collisions and punctures like the one responsible for the 2013 Tesla fire in Washington. Tesla now says its redesigned titanium underbody shield cuts the chances of a battery fire caused by damage to “virtually zero.”
  • EV battery cells are segmented by firewalls, which contain or at least slow the spread of a fire, buying time for the driver to pull over and exit the vehicle.

 

Battery packs from the Tesla Model S

Battery packs from the Tesla Model S

Since plug-in vehicles made their first push into the mass market in 2010, reports of battery fires (at least in countries with strong product safety standards) have been rare—and getting rarer.

The same can’t be said for internal combustion engines. According to 2010 study by the National Fire Protection Association, ICEs account for an average of 287,000 vehicle fires per year. What’s more, the danger resulting from a burning gasoline-fueled car is likely much greater. The total potential energy stored in fully charged Nissan LEAF is equivalent to less than a gallon of gasoline. Where ICEs are known to fully explode on impact in some particularly violent crashes, the worst-case scenario for an EV is that one or more segments of its battery pack catch fire before gradually spreading.

Though there hasn’t yet been a definitive study of EV fires in the United States, the available evidence suggests that driving an EV could be your best defense against fatalities, injuries, and property damage resulting from vehicle fires.

The Built-in Safety Benefits of Plug-in Cars

Nearly all electric vehicle models sold in North America meet or exceed the safety ratings of the leading gas-powered vehicles in their class. Part of this has to do with a tendency on the part of carmakers to load plug-ins with more standard features as a way to making their higher sticker prices more palatable to consumers. For example, the Nissan LEAF comes with an advanced air bag system and electronic stability and traction control, while other non-luxury sedans generally do not. But there are also several benefits that are inherent to the technology.

While it’s widely known that the extra money you pay up front for a plug-in tends to come back in the form of fuel savings down the road, it will also pay dividends in fleet safety—which can, in turn, add up to real dollars in terms of insurance and accident costs.

In most modern electric vehicles, heavy battery packs sit below the passengers—making them easier to steer and better for fleet safety.

In most modern electric vehicles, heavy battery packs sit below the passengers—making them easier to steer.

The Heavier the Better

One of the first things you’ll notice about driving an EV is how much differently it handles. Hairpin curves are less jarring and the sensation that your car is tilting or rocking as you enter or come out of a turn isn’t there. To fully understand the reason behind this difference might require dusting off your old college physics textbook, but the simple answer is that it comes down to weight distribution.

Thanks to the massive battery packs required to store the energy that makes them go, plug-in vehicles are significantly heavier than gas cars. This in itself is a major safety advantage, as heavier cars tend to “push” lighter ones in the event of a collision, causing the distribution of force to be more favorable to passengers of the more massive vehicle. From the standpoint of accident avoidance though, the real benefit of an EV is that most of its weight is kept low to the ground and distributed more evenly.

This helps to prevent rollover, which is a particularly deadly and at times unpredictable variety of accident. According to NHTSA, rollovers account for more than a third of all accident fatalities despite making up just 2.1 percent of total accidents.

Rollovers are particularly common in SUVs, which tend to ride higher off the ground and have taller cabins. Nevertheless, thanks primarily to battery weight distribution, Tesla says its engineers tried to “flip” the Model X SUV in safety tests but couldn’t.

Chevrolet Volt rollover test

Chevrolet Volt rollover test

Maintenance Benefits Contribute to Safety

Maintenance issues can also factor into fleet safety. While EV proponents often trumpet their lower maintenance costs thanks to fewer moving parts and no particulate buildup in the engine, the impact this has on safety is usually ignored.

The most important maintenance benefit from a safety standpoint comes from reduced wear and tear on a plug-in car’s brakes. Thanks to regenerative braking systems—which capture and restore energy that would otherwise be lost to friction—EVs end up putting much less of a strain on their brake pads. This saves owners a little money in maintenance costs, but occasionally, it could also save lives.

A Safer Plug-in Fleet

We’ve established that electric vehicles don’t pose significant added safety risks compared to conventional cars and trucks. In fact, there are many ways in which they’re a whole lot safer.

Fleet safety neither begins nor ends with a purchase decision, though. Next week, we’ll look into the best strategies for maximizing the safety of your plug-ins vehicles and charge infrastructure (update: link has been added).

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  • canuckinaz

    Great article, Zach. One other thing that is worth mentioning for EV safety is that in the event of an accident where a first responder needs to access the vehicle, perhaps with the “jaws of life”, that the battery pack may be damaged structurally but still have a significant amount of voltage. This can cause a hazard to the first responders who may be unfamiliar with this danger.