New Study of E-Scooter Injuries Raises More Questions than it Answers

Photo: Nathan Rupert/Flickr
Photo: Nathan Rupert/Flickr

How dangerous are e-scooters? The question has become pressing as they’ve proliferated all over the country, and researchers are scrambling for answers.

A new study published in the Journal of the American Medical Association [PDF] attempts to add some numbers to the discussion. But it doesn’t do much to make the situation clearer.

The paper examined the number of e-scooter related injuries treated at two UCLA-affiliated emergency rooms in Santa Monica, California, which has been called the epicenter of scooters and e-bikes in the U.S.

Between September 2017 and August 2018, the two ERs treated 249 people for e-scooter related injuries. Of those, 15 were pretty serious — requiring a hospital stay — and two required intensive care. Some of the injuries do sound a bit gruesome, one person was admitted with brain bleeding and another with cervical spine fracture.

In addition, the study showed that there are a fair amount of young people using the scooters, even though that violates the Bird’s policies. About 11 percent of those seen at the ER were under 18.

The JAMA article makes an argument in favor of helmet mandates.

But the scooter companies are pushing back. The study doesn’t attempt to measure exposure in a thorough way, so it’s hard to determine if the number of injuries recored should concern us. Bird corporate says “millions” of rides were taken in Santa Monica during the study period.

The researchers do note that during the same time frame, 195 bicyclists and 181 pedestrians were treated for injuries.

The most common injury was a head injury; about 40 percent of the injuries scooter riders had a head injury, compared to about 20 percent with fractures.

We asked Kay Teschke, a public health researcher at the University of British Columbia who was studied bike helmet issues, if she could help us make sense of the study. She agreed that it was hard to draw any firm conclusions.

“To understand scooter injuries, studies should allow comparison to other modes,” she said. “Ideally, there would be an exposure denominator to allow calculation of the risk of injury, that is, the number of emergency department injuries per trip or per mile travelled. This could be compared to the risk of other modes of travel, including walking, cycling, driving, transit.”

On background, Bird said the researchers did not contact the company for ridership data.

Requiring scooter companies to provide helmets might not be as simple as public health researchers imagine however. Boston experimented with a helmet vending machine for its bike share system, but it was short lived. It requires a lot of equipment and sanitation issues and is a difficult problem to solve. In the end, most cities abandoned the idea of providing helmets for bike share in part because bike share, anyway, has proven to be very safe.

Research shows that helmet requirements discourage bike ridership, which in turn can make biking more dangerous by reducing the safety in numbers effect.

14 thoughts on New Study of E-Scooter Injuries Raises More Questions than it Answers

  1. But every mayor who has them has told Mayor Durkan not to allow them because they are too dangerous. You can’t argue with anecdata. Especially 2nd hand anecdata which may possibly just be completely made up.

  2. Yeah, I read the original study trying to figure out if the brain hemorrhage and the spine fracture were the result of something that a helmet would not have protected against, like being hit by a car, and could not find the information.

    The language used in the study made it clear that the authors started with a goal rather than following where the data led them.

    That’s unfortunate because it sure looks like what it actually shows is that if you’re going at under 15mph, the max speed of a scooter, your head injuries rarely result in even an overnight stay. That would be an interesting finding.

  3. It’s almost like most people don’t get severely injured when they fall down at the speed of sprinting – like humans were made to not die while chasing something. Weird.

  4. We do need to compare scooter injuries to other modes to draw policy conclusions. Scooters might be safer or riskier than other modes. The only way to know is to compare the modes in a way that accounts for risk exposure.

    But what metric should the comparison use? Injuries per trip is useless. A trip can be very long or very short or anything in between. There can be a lot of exposure in one trip or just a little exposure. Injuries per trip tells you nothing about exposure.

    Injuries per miles driven isn’t much better. Say a car in city traffic covers 3 miles in 9 minutes (going 20 mph). A scooter might cover 3 miles in 24 minutes (going 7.5 mph). Now say they both have an injury during those trips. The injuries per mile driven metric would say they are equally dangerous. But the scooter had two and a half times more exposure in terms of actual time traveling. It was two and a half times safer in terms of exposure time.

    So a good metric for this type of comparison is injuries per amount of travel time. With that metric, you can compare all modes of travel on a reasonably equal basis.

  5. I think it’s too early to make conclusions since some many of these trips are by novices that aren’t used to riding them yet. But it might be a good idea to further limit their top speeds, particularly where there’s a lot of sidewalk riding. Most of these are limited to 15 mph I believe, maybe 10 or 12 mph would be better. They can’t be too slow as it could hurt ridership .

  6. I do agree that it’s too early to make conclusions. I also agree that maybe the speeds the scooters can reach is too great. I suspect though, that we will never know the whole story- just like Uber and Lyft, who refuse to turn over any of their “proprietary data,” we will never really know how much these scooters are being used. If, like in the article, they were “consulted,” I’m sure the result would be to lessen the reality of how many people are getting hurt. Just like the ride-sharing companies, they’ll say “trust us” to white-wash whatever the latest issue is.

    And for any sidewalk riding? Riding those things on the sidewalk in SF is illegal. The rider should get a massive fine for doing so, just to make the point that it should never be done.

  7. Angie,

    Only one of the Emergency Rooms is in the City of Santa Monica, the other is a few miles away in the Westwood area (by the actual UCLA) of the City of Los Angeles. It is odd that the other ER in Santa Monica, Providence St. John’s, was left out of this study.

  8. Could the parallel numbers for Santa Monica be presented?

    How many people came to ERs due to incidents involving automobiles and trucks?
    How many people were injured in their bathrooms/toilets/showers?
    What were the numbers for bicycle users in this same period, and what where they like in the year before, when trips that were made by eScooter might have been made by bicycle, or by car, or not at all?

  9. Excellent point. This has been a long-standing issue and it is disappointing that Kay Teschke would reference miles traveled. It inherently skews that data against human powered modes because one can travel much farther in a motor vehicle. Even two people biking the same route will have different exposure based on how long each is taking to make that trip (i.e. exposed to more traffic). Time is the most accurate means to normalize exposure and risk for different modes.

  10. In defense of miles travelled as a metric, travel is very often for the purpose of getting between specific places, and the constant there is distance. I don’t commute to work for X minutes, I go Y miles. Consider your car/scooter example as applied to someone commuting; is it really useful to say that they are 2.5x safer on a scooter?

    More importantly, do you think policy outcomes would be better with that metric? In SF, for instance, I’m much more likely to be seriously injured or killed if I walk or bike to work every day than if I drive. I think that’s a problem that should be addressed with better bike and pedestrian infrastructure, but your metric would minimize the way that risk was reported. I’d rather not use a metric where we are in effect telling people walking: “Well, it’s true that you’re more likely to die if you don’t drive to your destination, but since it will also take longer we’re going to call it safer.” I don’t see that leading to policy decisions that reduce pedestrian deaths.

  11. Stuart, the metric is best for comparing the amount of risk that a given amount of travel poses to an individual. It could be used to make regulations and policies about specific modes. For example, if scooter riders are getting skull injuries at rates like motorcycle riders, then we might consider requiring helmets. If scooter riders are getting skull injuries at rates like pedestrians, then we might discard the idea of helmets.

    Other metrics are better for other purposes. If the goal is Vision Zero, then the guiding metric is the raw numbers of injuries and fatalities. In the city of San Francisco, that will lead to a focus on pedestrian safety, and vehicles won’t get much attention. In an auto-oriented suburb, that will lead to a focus on vehicular safety, and pedestrians won’t get much attention.

    If policymakers want to compare San Francisco’s traffic safety to other cities and suburbs, then a good metric is injuries or fatalities per capita. The per-capita metric is best measuring for systemic traffic risk at the level of communities, states, nations, and so on.

  12. I’m not even sure if time is the right normalization. My instinct here is to say to go with something like “injuries per 1,000 trips”–neither the amount of time nor the distance traveled are really what matter here. What matters is how likely you are to get injured during a typical trip, so going with a per 1,000 trips metric seems better than getting bogged down trying to figure out how to explicitly account for various factors like traffic, distance traveled, etc when they’re already implicitly accounted for in the injury rates.

  13. It’s quite true that an estimate of the risk per mile or per trip is requisite to start drawing comparisons between the risks of electric scooters versus other forms of transportation; I trust that such estimates are on the way.

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