How safe are e-scooters?

Last week, Council members Mosqueda and O’Brien staged a rally for to promote introducing electric scooters to Seattle. They even invited leading scooter-share companies Bird and Lime to sit at the committee table in Council Chambers and give a nearly uninterrupted sales pitch — with no hard questions following.

Mayor Durkan has been much more pessimistic on the idea, frequently citing the number of mayors who have told her to resist e-scooters as long as possible because of the injury rate.

Before Seattle gets into the e-scooter game, shouldn’t we know something about how safe they are? Let’s dive in and look at the stats.

Let me just say up-front: if you are expecting a yes or no answer to the question “Are scooters safe?” you’re going to be disappointed. There simply aren’t enough reliable studies — and quite frankly, there aren’t enough scooter-miles driven — to give a clear, statistically significant picture. These is enough, however, to give us a general sense of what the issues are and what should be done to address them.

I would also caution against relying heavily on safety information from the companies in the business; having reviewed Bird’s recent self-published safety report, I can tell you can it’s mostly a marketing/public policy advocacy piece and many of its safety statistics seem to be cherry-picked and/or taken out of context. But we’ll come back to that.

There are three limited studies of e-scooter deployments in U.S. cities that are worth paying attention to:

  1. Austin, Texas. E-scooters first started appearing on the streets there in April 2018, and last fall Austin Public Health did a study on the injury rates. Their results were published earlier this month.
  2. Santa Monica, CA.  Researchers tracked scooter injuries in the Santa Monica area over a one-year period from September 2017 through August 2018.
  3. Portland, Oregon. Concurrent with a four-month e-scooter pilot last fall, the Multnomah County health department tracked scooter-related injuries. Its finding were incorporated into a more expansive report on the pilot by the Portland Bureau of Transportation, who presented to the Seattle City Council at last week’s O’Brien/Mosqueda scooter rally.

Here are some of the qualitative findings that are consistent across the studies.

  • The vast majority of injuries (80% or more) don’t involve collisions with motor vehicles, pedestrians, or bicycles: they are simply riders falling off their scooter or driving it into an inanimate object.
  • A large fraction of injuries happen on someone’s first ride on the scooter.
  •  30-50% of the injuries are head injuries, with a significant fraction of those showing indications of concussion or traumatic brain injury. On a related note, almost no scooter riders (around 5%) wear helmets — even when they are required by law.
  • 5-10% of injured riders were intoxicated.
  •  5-10% of injured riders were underage (under 18).
  •  Most of the injuries were minor enough that the person was discharged directly from the Emergency Department/urgent care center and sent home.

A quantitative comparison of safety statistics is trickier. Both the Portland and Austin study estimate injuries per mile ridden, and come up with nearly the same rate: around 2.2 injuries per 10,000 miles (those injuries serious enough to require a visit to urgent care).  So how does that compare to other modes of transportation? The federal government publishes nationwide data on bicycle, motorcycle, and motor vehicle fatalities and  motor vehicle injuries. They also publish estimates of total miles driven for motorcycles and motor vehicles — but not for bicycles, and after hours of scouring the Internet, I came up empty on an estimate for annual bicycle miles ridden in the U.S. (if anyone knows where I can find such stats, please let me know and I will update this article)  But let’s look at what we can, knowing that we will get an incomplete but hopefully useful picture.

According to published statistics, in 2017 there were 3.213 trillion motor vehicle-miles driven in the United States, resulting in 4.6 million injuries and 37,132 fatalities. That’s .014 injuries per 10,000 miles — 150 times lower than the scooter rate. Now before you start citing that number to everyone (assuming it fits your preferred narrative on scooters), keep in mind that the statistics for scooters are unreliable because the sample size is small. To make this clearer, let’s look at fatality rates instead, and note that none of the three scooter studies logged any fatalities. Austin’s study logged 891,000 miles ridden, which is tiny compared to the 3.2 trillion motor vehicle miles driven in 2017. If we do the math, we discover that the motor-vehicle fatality rate is .011 per million miles. In Austin we saw zero fatalities in nearly 1 million scooter-miles, and we would also expect to see zero  fatalities after 1 million motor-vehicle miles. Because the fatality rates are so low, without a larger sample of scooter miles, we really can’t see what’s going on here.

Let’s pause for a moment here. As we work through the statistics, it’s easy to lose sight of the tragedy represented by any and all traffic fatalities. It is absolutely not the point of this exercise to come to a conclusion about what is an acceptable traffic fatality rate — or injury rate, for that matter. The only acceptable rate is zero. What we are doing here is trying to separate out what we know from what is still beyond our understanding, so we can make smart, informed personal and policy choices.

In case you’re curious, the motorcycle fatality rate is .25 per million miles, based on 5172 motorcycle fatalities over 20.149 billion miles driven. That’s still not a clear distinction from the scooter statistics.

So the conclusion here is that based on the limited studies on e-scooters, we can’t tell if they are more or less safe than motorcycles or motor vehicles, though there is a hint that their injury rate is higher than motor vehicles. Despite the zero deaths reported across the three studies, there are, in fact, reports of deaths and other near-fatal collisions involving scooters, not all of which necessarily involved motor vehicles, so it’s hard to draw conclusions about scooter fatalities either.

But the studies tell us some other things about e-scooter use and safety. For instance, we know that e-scooter users have a strong preference for protected bike lanes and bikes lanes that have a large separation from vehicle traffic, and the higher the speed limit on a road, the more likely it is that scooter riders will move from the road to the sidewalk — even when it’s illegal and causes problems for pedestrians. On a related note, we also know that, similar to the problems with bike-share we already see here in Seattle, scooters left blocking sidewalks create obstacles for all sidewalk users but especially for those with physical disabilities. In an ideal city, there is a full, connected network of protected bike lanes that keep scooters safe while also keeping them off the sidewalks. That doesn’t imply that the scooter injury rate will plummet; remember that the vast majority of scooter crashes don’t involve another vehicle. But it might reduce the severity of injuries, and it will certainly make scooter (and bicycle) riders feel safer.

O’Brien said an interesting thing last week: one of his reasons for wanting to push for scooter share now is to add more pressure on the city to build out a complete network of protected bike/scooter lanes faster. He is certainly right in recognizing the chicken-and-egg problem: when a city such as Portland has a large and active biking community, the existing bike network is closer to reaching capacity and the city responds to that demand by building more bike lanes. But on the flip side, if bike and scooter riders don’t feel safe riding for lack of those lanes, it’s more challenging to reach a critical mass of riders that can effectively drive the demand. The scary part of O’Brien’s intent, though, is that he knows that Seattle’s current incomplete, partitioned bike network will not be safe for an influx of scooter riders — though the riders will benefit to some extent from the “safety in numbers” effect wherein the presence of more riders raises the visibility and awareness of all of them and thus makes all of them incrementally safer.

Another intesting aspect of e-scooters that O’Brien was very excited about is its potential for “mode shift” from personal vehicles or ride-hailing (Uber/Lyft). Portland collected data on this question during its study, surveying riders as to how they would have made their most recent scooter trip if the scooter was not available. 36% would have walked; almost 9% would have taken public transit, nearly 18% would have driven a personal vehicle, and almost 20% would have hailed a ride.

That certainly raises the opportunity to reduce motor vehicle traffic, but what’s less clear is how much of an environmental benefit there is. E-scooters need to be charged, so their carbon footprint depends heavily on the source of the electricity (and sadly, they get mostly get charged at night, which means that it probably isn’t solar energy). But on top of that, it’s still unclear what the carbon footprint is of the operational side of scooter-share operations: the data center running the cloud service, as well as the fleet of vans picking up, dropping off, and repositioning scooters. Bird and Lime have not provided any information on that issue yet (though O’Brien and Mosqueda did ask for it).

Even when they do, there’s every reason to be distrustful of the information that these for-profit companies provide — including their safety statistics. For example, Bird’s self-published safety report doesn’t stand up well to close inspection. Their injury statistics are generated from injuries that their riders report directly to them through their own app. They claim an injury rate in Austin of 32.8 per million miles (or .32 per 10,000 miles), an order of magnitude off from the figures published by Austin Public Health.

They also published a bizarre, apples-to-oranges comparison of absolute numbers of ER visits between scooters and bicycles (or pedestrians+bicycles), without presenting any information about the population of pedestrians, bicyclists, and scooter riders.

And another, comparing pedestrian fatalities by mode, knowing full well that this is a meaningless comparison given how few scooters are out there and how many other vehicles are.

They also pulled a quote from the Portland injury study out of context.

Here’s the full quote from the report, in context:

Like all parts of the transportation system, using e-scooters
entails risks. For any injury hazard, we would expect injuries to increase as exposure to the hazard increases. That is what we observed during the e-scooter pilot program.

The number of injury visits from scooters is small relative to total crash injuries, and many of the injuries were not severe. It may be the case that the rate of injury per mile, or per trip, is high compared to other modes, but we don’t have enough data to make that conclusion. However, we did not find evidence of a number of injuries so large or of such severity that it would discourage further pilot programs in the City of Portland. Future evaluation should focus on characterizing the severity of injury. Monitoring injuries could be streamlined by focusing on the age group.

Even Brianna Orr, last week’s presenter from the Portland Bureau of Transportation, had trouble presenting data in context — though I will give her credit for being level headed and even trying to be a voice of reason and restraint when Council member Mosqueda started pushing for deploying an e-scooter share pilot in three weeks. She presented this slide of weekly scooter-related ER visits during their scooter pilot last fall:

O’Brien immediately jumped on this as potential proof that once people get practice in riding a scooter, the injury rate goes down, a notion supported in theory by the high proportion of injuries for first-time riders. But digging through the final report from her pilot, I found this graph of weekly scooter trips and miles:

That provides critical context for the injury reports: as usage dropped off toward the end of the pilot, naturally so did injury reports. It probably doesn’t entirely explain the drop-off in injuries, but it explains much of it.  Here’s further corroborating evidence: the number of complaints received per week also dropped off as participation in the pilot waned.

Here’s the bottom line: we still know very little about the safety of e-scooters. What we do know is that they are safest when they have separated or protected lanes to travel in that protect them from motor vehicles, and sidewalk pedestrians from then. Still, scooter riders are perfectly capable of creating their own crashes without the involvement of anyone else. They rarely wear helmets, and as a result they when they do get injured they frequently end up with head injuries.

It’s no wonder that the city’s policymakers span the spectrum of views on allowing e-scooters on the streets of Seattle. Mosqueda wants to push ahead at light speed — though she herself admitted that she doesn’t wear a helmet when she rides bike share in Seattle or when she tried an e-scooter on a visit to Portland (she does wear a helmet when she rides her own bike), and that on her first e-scooter ride in Venice Beach, she rode it into a garbage can. As mentioned earlier, O’Brien wants to push forward (though not necessarily as fast as Mosqueda) to drive mode-shift and to put more pressure on SDOT to build out the bike network faster. Mayor Durkan, for her part, had been staunchly opposed to scooter-share, but then last week released an op-ed saying that she was willing to move forward under certain conditions — probably non-starters for Bird and Lime, such as indemnifying the city from liability for rider injuries.

If scooter-share does move forward, we can look forward to some heated debates about required helmet use, when it’s permissible to ride a scooter on the sidewalk, mandatory training for scooter users, and of course scooter parking. Because if there’s one thing this city loves, it’s arguing about parking.


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  1. It’s a great article as far as it goes, but it doesn’t discuss the key issue. What were the increased payouts of tax money in Austin, Santa Monica, and Portland from those scooter accidents? I.e. The City did not exercise due care in the adoption of its regulations on scooters, where they are permitted, etc. The City, in authorizing scooters on sidewalks, did not engineer or maintain them with due care to prevent people from falling off. People sue from walking and falling over issues of maintenance, design, etc. How many more people will fall on scooters vs. walking, if any? How much higher will the dollar claims be because of the increased speed, height off the ground, etc. What would we rather spend those dollars on? The homeless? More police? More affordable housing? Parks? Bike lanes?

    1. Given how recent these studies/pilots were done and how new scooters are to most places, it’s far too early to get data on that. Claims and litigation take several months, if not years, to work their way through.

      1. So there is no news or data worth having at this time.
        So no story. Safety has never been the issue. Durkan has not framed it that way. How much do the accidents cost the taxpayer if the city legalizes scooters has always been the concern.

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