Tiny Vehicles and the New Safety in Numbers

New York City Council Member Robert Cornegy test drove a Bird scooter in New York recently. Photo: Gersh Kuntzman
New York City Council Member Robert Cornegy test drove a Bird scooter in New York recently. Photo: Gersh Kuntzman

With dockless bike share systems and electric scooters rolling into cities across America at an unprecedented rate, a holistic reduction in crashes, fatalities, and injuries should follow. Peter Jacobsen, author of the seminal “safety in numbers” theory of traffic safety, with his brother Joel Jacobsen, looks at how masses of tiny vehicles work towards Vision Zero.

On any weekend night in Washington, D.C.’s trendy Adams-Morgan neighborhood, you can spot — amidst the laughter and loud music — crowds of people traveling between blocks of restaurants and bars. You might notice some heads gliding along the wide sidewalks at twice the pace of others. Those folks are riding the electric scooters that, in a remarkably short time, have become ubiquitous in many urban neighborhoods around the country. First, we had tiny houses. Now, we have tiny vehicles.

The first generation of shared public bicycles were rented from a sidewalk rack, a system familiar from airport luggage carts. Newer, dockless shared bicycles instead use a smartphone app to direct the user to the nearest bike, which can then be left anywhere for the next user to find. Battery-powered scooters, grown-up versions of the children’s ride with a small electric motor installed, rely on a similar phone-managed dockless system.

Two decades ago, the very idea of sharing vehicles with strangers would have struck most Americans as odd, even outlandish. Twelve years had to pass after Zipcar was founded in 2000 before even 3% of Americans had tried driving a shared car. But then, shared cars aren’t visually distinctive. The installation of bicycle docks, by contrast, provided a constant visual reminder of the possibility of a shared ride, getting urban-dwellers used to be the idea. The dockless versions trumpet their convenience everywhere they’re left. Americans’ growing comfort with shared rides is reflected in the uptake rate for electric scooters, which flew past the 3% mark in less than 12 months.

It’s not hard to understand scooters’ appeal. Compared to other urban transport options, they’re cheap, typically requiring just a dollar to start. They’re convenient, needing no parking spaces. And, because they add little to congestion and produce zero tailpipe emissions, they can be ridden with a clean green conscience.

But what does the proliferation of tiny vehicles mean for traffic safety? Do they bring us closer to achieving the goal of Vision Zero, or are they just a faddish sideshow of no real consequence?

The answer begins by considering falling off one of the many new tiny vehicles on the street.

Any physical movement involves some risk of falling, of course. A recent New York Times article interviewed emergency room doctors, who are treating increasing numbers of scooter injuries, ranging in severity from skinned knees to head trauma. The San Francisco Department of Public Health is inaugurating a plan to collect injury data.

While we currently lack figures about scooters in particular, long experience has shown us that in an urban setting, walkers and bicyclists are unlikely to be injured fatally – unless they’re hit by a motor vehicle, when the likelihood of serious injury instantly zooms. It seems reasonable to expect similar effects with scooters. Falling from a scooter rolling along at its top speed of 15 mph is doubtless painful, but nothing at all like being hit by a 4,000 pound hunk of metal hurtling at 30 mph or more.

However, a narrow retrospective focus on injuries incurred overlooks the possibility of injuries prevented. Strong empirical evidence suggests that the best thing we can do to ensure the safety of scooter riders is to increase their number. We have no shortage of data about pedestrians and bicyclists, and there’s every reason to expect the experience of tiny urban vehicles will follow the pattern. The risk to walkers and bicyclists of being hit by a car decreases rapidly where more people walk and bike. Simply put, there is safety in numbers. Where three times as many people walk and bicycle, the risk to walkers or bikers halves. Even better than that, cities that encourage more bicycling with infrastructure changes experience a decrease in the raw number of bicycle injuries, and cities that implement bike share programs also see a reduction in the number of bicycling injuries. The five major cities that introduced bike share had a 28 percent reduction in injuries.

These findings, which may at first seem counter-intuitive, are a product of human perception. Our brains, which evolved over the long millennia before cars were invented, are too efficient for our own good. We scan our landscapes, as our hunter-gatherer ancestors did, for the common hazards, not the rare ones. There is little reward in devoting mental energy to a search for things we’re highly unlikely to see, and so our visual cortex generally doesn’t. Consequently, in cities where bicycles and pedestrians are rare, drivers are slow to perceive them. And at automotive speeds, “slow to perceive” is almost the same as not perceiving.

Moreover, this “low-prevalence effect” is unrelated to size. In places where motorcycles, and even buses, are rare, drivers find it disturbingly hard to perceive them. As pedestrians, bicycles, motorcycles, and buses become more common – as they move into the category of “known hazards to be scanned for” – the risk of collision steadily sinks.

There’s no reason to believe the low-prevalence effect will exempt electric scooters and other tiny vehicles. But by the same token, there’s likewise no reason to believe they won’t benefit from safety in numbers. As tiny vehicles become more common, motorists will increasingly be on the lookout for them. More rapid motorist perception will translate into fewer collisions.

Not only that, but as the number of urban scooters increases, collisions will likely become less severe. In places where pedestrians and bicyclists are common, motorists’ collisions are not only rarer but less likely to be lethal, presumably because motorists slow down, reducing the kinetic force involved in the collisions that do occur.

The proliferation of tiny vehicles also has the potential to encourage more people to leave their cars at home, at least for short trips. Motorist deaths vary on a nearly one-to-one basis with motor vehicle use. The fewer car trips, the fewer driver deaths. If drivers can be persuaded to hop on scooters for everyday errands, we’ll be that much closer to Vision Zero.

Over time, street design will likely adjust to better accommodate tiny vehicles. Their small size might give them a political advantage over bicyclists, who require relatively more space and have had to fight long years for the precious inches of asphalt cities grudgingly dedicate to bike lanes. Although it’s hard to predict what accommodations experience might eventually show are best suited to tiny vehicles, they are unlikely to involve that same scale of trade-off.

Already tiny vehicles offer the benefit of fun. They promise serious benefits, too. Their advent may be the best thing to happen to the Vision Zero movement since the separated bike lane.

This article is published as part of the Vision Zero Cities Conference, November 7-8 in New York City. Register for the conference.

Peter Jacobsen is a professional engineer with a strong interest in the health impacts of transportation policy. His published work ranges from injury prevention to activity promotion. Joel Jacobsen is the author of two books and writes a regular business law column for the Albuquerque Journal.

FOOTNOTES

“The Micro-Mobility Revolution: The Introduction and Adoption of Electric Scooters in the United States” Populus Research. https://www.populus.ai/micro-mobility-2018-july
“Health Officials Prepare to Track Electric Scooter Injuries,” Bradley Berman, The New York Times (Aug 2, 2018)
“Safety in Numbers: More Walkers and Bicyclists, Safer Walking and Bicycling.” Jacobsen, Peter. Injury Prevention https://doi.org/10.1136/ip.9.3.205.
“Infrastructure, Programs, and Policies to Increase Bicycling: An International Review.” Pucher, John, Jennifer Dill, and Susan Handy. Preventive Medicine https://doi.org/10.1016/j.ypmed.2009.07.028.
“Global Bike Share: What the Data Tells Us about Road Safety.” Fishman, Elliot, and Paul Schepers. Journal of Safety Research https://doi.org/10.1016/j.jsr.2015.11.007.
“Safety in Numbers for Walkers and Bicyclists: Exploring the Mechanisms.” Jacobsen, Peter Lyndon, David R. Ragland, and Charles Komanoff. Injury Prevention https://doi.org/10.1136/injuryprev-2015-041635.
“Safety in Numbers: Target Prevalence Affects the Detection of Vehicles during Simulated Driving.” Beanland, Vanessa, Michael G. Lenné, and Geoffrey Underwood. 2014. Attention, Perception & Psychophysics https://doi.org/10.3758/s13414-013-0603-1.
“Evidence on Why Bike-Friendly Cities Are Safer for All Road Users.” Marshall, Wesley E., and Norman W. Garrick. Environmental Practice https://doi.org/10.1017/S1466046610000566.
“The non-linearity of risk and the promotion of environmentally sustainable transport.” Elvik, Rune. Accident Analysis and Prevention. https://doi.org/10.1016/j.aap.2009.04.009
  • Michael

    I think most Americans in urban areas suffer from the same problem that about 10-20% of their trip is white knuckle riding, even after strategically scouting the route ahead of time. Just taking the most direct route, probably results in 35%+ of the route being unnerving. Numbers certainly help, but at the end of the day, riding a scooter unprotected next to an 80,000 lb semi or high speed cars is always going to be frightening to the vast majority of people. We need to get a lot smarter about developing an inventory of the key pain points in our bike (& now scooter) networks and articulate why having a comprehensive networks is worth the trade-offs, whether that’s taking space from travel lanes, parking, bus stops, even sidewalks. In top 20 metros, gridlock slows traffic enough that biking & scooters can keep up so riding in traffic kind of works. Outside of those metros, vehicles are driving 30-40+ mph on urban surface roads. Numbers won’t fix that.

  • Jersey City’s new protected bike lane experiment actively welcomed scooters, roller bladers and skateboarders.

  • Cynara2

    Your war on pedestrians just has no limits, does it? The first paragraph encourages riding these on the sidewalk.

  • Cynara2

    They made it clear in the first paragraph of this article, and with the photo, that they are encouraging ruining the sidewalks for pedestrians, as usual.

  • ATK87

    No it doesn’t. I just makes an observation that people are riding these on sidewalks and then goes on to explain that streets are not designed for scooters, thereby implying that their use on sidewalks is a reaction to the lack of accommodations for small vehicles on the street itself. It doesn’t condone their use on the sidewalk.

  • com63

    haha. Pedestrians, Scooterists and Cyclists must band together against cars!

  • meelar2

    We need to cut our carbon emissions by 40% in the next 12 years, and eliminate them by 2050. We won’t do that by sticking with the existing paradigm or just preserving our existing gains. We need a dramatic transformation of our entire infrastructure, and you pitting scooters against pedestrians–when the real enemy is the cars that make both modes more dangerous than they need to be–is totally unhelpful to that goal.

  • crazyvag

    I agree. Both scooters and pedestrians deserve protection from vehicles. Pedestrians arguing against scooters on the sidewalk would be better served by arguing for safe bike lanes.

  • crazyvag

    I don’t see it that way. It’s a push for space for scooters and riding scooters on sidewalk are simply a reflection of pedestrians and riders being lumped into tiny space.

  • Gridlock trying to pick-up or deliver freight or fresh food is one reason why the cost of living is so high among the top 10 cities. Some roads may not be safe for unprotected riders to ride alongside heavy trucks.

    In-fact Federal Highway Administration roadway design standards for Designated Truck Routes and Principal Arteries demand a roadside clear zone that is designed for emergency collision avoidance use at speed and is supposed to exclude both street parking and unprotected riders.

    In the urban area I grew-up in, an urban area of 4.5 million people in 1970, it was quite common to have urban surface boulevard traffic moving at 65 mph across all 8 lanes of traffic in the early 1970s. Even 5-lane arteries were often posted at 40-45 mph in the suburbs also.

    The way I feel about it as a longtime professional driver, truckline owner, and freight transport and warehousing planner is that powered scooters and bikes really don’t belong on the same roads that heavy trucks drive on for a wide variety of reasons.

    Who has the right of way, the 18-wheel truck turning right or the bicyclist that ignores the truck’s turn signals and tries to pass the truck on the right while the driver is turning right?

    The answer is quite simple really. The truck driver has the right of way because riding alongside an 18-wheel truck the truck driver can’t see you there except close to the truck near the back of the trailer, and unfortunately, with trucking deregulated and heavy trucks getting paid less than regulated taxicabs, there isn’t any money for collision avoidance radar.

    You don’t want to get hit by a heavy truck or bus that is turning right? My advice is to stay back and yield to the turning vehicle’s turn signals.

    If you are riding alongside a heavy truck more than 3-4 away from it or forward of the trailer landing gear legs, and the truck’s signal lights start flashing on your side, just remember that the truck driver can’t see you there, and then take immediate evasive action to avoid getting hit. I recommend braking so that the trailer tires don’t run you over.

    If you don’t want to get taken-out by vehicles turning at intersections I would also recommend not riding the wrong way on one-way streets.

    Also remember that without brake lights that it takes a loaded 18-wheel truck or bus about 4 times as long to stop from 15 mph or 25 mph as it takes your bicycle or scooter to stop in, including following driver reaction time.

    Legally you are required to use hand signals in-lieu of signal lights 100-feet in-advance of turns and when stopping too. This graphic below shows legally-required hand signals that bicyclists are supposed to use according to the New York State DMV.

    [Quote] Bicyclists also must: Signal turns, lane changes and stops through the use of the hand signals shown. A bicyclist can signal a right turn when they extend the right arm straight out to the right. [End quote]

    https://dmv.ny.gov/sites/default/files/styles/panopoly_image_original/public/bikehandsignals.png?itok=tvUmsa1e

    https://dmv.ny.gov/about-dmv/chapter-11-sharing-road

    I suspect that the same hand signals should be used by e-scooter riders too.

  • Cynara2

    You are talking gibberish. You just justified taking your problems with cars out on pedestrians.

  • Cynara2

    No. Pedestrians do not hate cars or drivers. All of you do. We are not part of your hate fest.

  • Cynara2

    That is a gigantic lie. The bike lanes do pedestrians absolutely no good. Every teenager will refuse to use the bike lane and go flying down the sidewalk. Why? To skirt the laws, just like their adult role models. No helmet? They will not want a ticket in the bike lane or a talk from the police. They will be torturing the pedestrians. And adults? They refuse to wait for a red light, stop for a cross walk or a stop sign. Give the best bike lanes in the universe and they will fly into the crosswalks and on the sidewalks to avoid following the motor vehicle laws. It is your attitude that is the problem. It has nothing to do with safety or infrastructure.

  • Cynara2

    That is a lie. Every single scooter I have seen so far has been on the sidewalk NEXT TO AN IDEAL BIKE LANE. cyclists and scooters use sidewalks and crosswalks to skirt the laws for motor vehicles, not for safety. You have a horrible attitude toward pedestrians, no matter what.

  • Cynara2

    I am pitting them against pedestrians? Typical of you to scapegoat pedestrians. It really is. Bike lanes are worthless to pedestrians. Absolutely worthless. Cyclists and e scooters just jump out of them in order to skirt the laws for motor vehicles. Just because they do not want to wait at a red light. Infrastructure will not change the hardness in your hearts. Why are you treating those of us with almost ZERO carbon footprint like dirt?

  • Cynara2

    They cannot signal. The left hand is used for signalling. E scooters have only a front brake and it is activated by the left hand. If they signal, they have no brakes. So, if they signal, it will mean that they cannot stop for pedestrians.

  • com63

    Drivers are the only ones who threaten everyone else. Scooters on the sidewalk may be annoying, but they won’t kill me. Drivers failing to yield to a pedestrian will.

  • com63

    Or you signal, then put your hand back on the brake. It’s like a football player making a fair catch. Signal for the fair catch, then lower hand and make the catch.

  • Cynara2

    That is a lie. Scooters will kill pedestrians on the sidewalk. It is only a matter of time.

  • Cynara2

    That is not how one signals. You do not withdraw your hand. You have no idea what you are talking about.

  • ATK87

    Show me where I condoned the behavior.

  • ATK87

    I’m sorry, but the last sentence had to prompt me to report your account and this comment. This is a place for dialogue and that is totally unacceptable.

  • Kyle

    Literally every article that mentions scooters on this blog that I have read has your inane pedestrian comments.

    Let’s all do ourselves a favor and just ignore the troll.

  • Michael

    I actually think walk/ped & trucking are huge allies. In an extreme example of Manhattan, less than 10% of trips are made in cars. Yet the place is inundated with cars, deliveries are totally dysfunctional. The buses crawl, peds & bikers aren’t happy. The problem – which seems obvious to me – is that the city has dedicated at least 75% of its street space to the 10% trips made in cars. Doesn’t work. Not there, not Boston, not DC, not Minneapolis. All the way down. Maybe it works in Orlando & smaller (for now). Right now, the 20 mile-plus radius of our top 30-40 cities are totally gummed up car traffic for hours everyday. That’s not an effective way to run an economy.

    The primary issue is that the average American is spending 50 miles per day in a car, circling around between work & discount shopping. There’s just no financially feasible way to build a country for 450M people with that driving pattern. We’ve done this happy motoring thing for 60 years & now we’re going to pivot to using those roads mostly for moving goods & food, while more & more trips are going to have to be made outside of cars. Or we’ll have to accept a less mobile, less prosperous future.

  • disqus_1pvtRUVrlr

    Show me on the doll where the bad bicyclist touched you Cynara.

  • disqus_1pvtRUVrlr

    “You might notice some heads gliding along the wide sidewalks at twice the pace of others. Those folks are riding the electric scooters…”

    Uhh, try 4 times the pace of others. And that is fundamentally a problem. Also, scooters introduce risks that simply are not as prevalent with walking or biking. The majority of crashes have not involved motor vehicles, thus your premise of safety in numbers is ridiculously flawed. A data point that bears this out is comparing shared scooters with bike share. The safety record of bike share in the US has been fantastically safe. Shared scooters? Not so much. It is inherent in the vehicle itself which is simply much less safe and controllable. Stop pretending that isn’t an issue.

  • Jake

    Yes, in the same sense that it’s only a matter of time before someone dies on a scooter from being struck by lightning. Americans die every year from being crushed by their furniture, it doesn’t mean that dressers are inherently dangerous.

    There are fundamental physics at play: a 10 lbs scooter going 15 doesn’t have the same momentum as a 2 ton vehicle going 50 mph. An 18-wheeler scooter isn’t going to drag you underneath and crush you. 50 000 Americans die each year from collisions with cars. Collisions with scooters, cyclists, roller-bladers, kids with wheely-shoes, etc., are statistical non-events, even in countries where they are way more prevalent. Why the moral panic over e-scooters?

    I think people are just more prone to moral panics over something that is new and unknown and therefore must be dangerous, over something that is familiar and convenient if unfortunately consistently lethal.

  • CarlessInOKC

    Why do you call opinions you disagree with lies? Honey, not vinegar, will help you catch more flies.

  • Stephen Simac

    As a pedestrian, I don’t want to share sidewalks with e-scooters zipping around us like an obstacle course because they are afraid of motor vehicles. Their top speed is unacceptably high for their limited stability and irresponsible rollout. They may not kill pedestrians, but have already injured many, although the main risk is to their riders. One hospital ER in SF reported treating 700 scooter injuries since they were scattered on the city’s sidewalks a little over a year ago. The safety in numbers only applies to increased motorist awareness with slower traffic speeds, enhanced by legal/visible road users.

  • c2check

    Where do you live/see the scooters on so many sidewalks? I didn’t notice any on sidewalks when I was recently in LA, Santa Monica, and San Jose (with the exception of the Ocean Ave sidewalk in SM, because scooters are not permitted in the beachfront bike lane despite its ample width)

  • SF Guest

    You’re comparing apples with grapes. Drivers failing to yield occurs on streets whereas scooters on sidewalks don’t belong there which is the concern.

  • Cynara2

    Which proves my point. You are dumping all of this on pedestrians and treating us like dirt, and then calling us evil if we object. If you have any courage, you might want to see what pedestrians are going through here:
    https://hooktube.com/watch?v=nWk89gk54dY

  • Cynara2

    https://hooktube.com/watch?v=gMNboHG5h5c
    Cyclists threaten and kill and cripple pedestrians. You cannot ignore this forever.

  • Cynara2

    https://hooktube.com/watch?v=gMNboHG5h5c
    No, pedestrians are panicking because this is what is going on where I live. There is no way you can pretend that these vehicles are not putting pedestrians through hell.

  • Cynara2
  • Cynara2


    They are killing pedestrians. The companies dumping them here are well aware of how dangerous they are. Pedestrians in Singapore are up in arms.

  • Cynara2

  • Stephen Simac

    Strange how even their test rider isn’t wearing a helmet, when they’re asking her to come to a rapid stop, likely to cause a fall. These companies won’t be the ones bearing the social costs of caring for disabled and head injured riders (or those they collide with}, who probably hopped on one, thinking they could save some time by not walking.

  • Daisy’s World

    The electric-scooter company Bird would lose half of its Raleigh fleet under the city’s proposed city rules. The rules would limit companies to 500 scooters each — Bird has about 1,100 across the city — and prohibit scooters from being parked in areas without sidewalks or where sidewalks are less than five feet wide, among other places. The rules cap the number of scooters allowed in the city at 1,500, but that would allow a third company here. The proposed 500 and 1,500 limits are based on what other cities have done including Charlotte, which allows a maximum of 300 scooters per company.
    City staffers are not recommending banning scooters — either forever or until the rules take effect In Seattle, the project there is called the Alaskan Way Viaduct Replacement, which reshaped what’s known as the SR99 corridor. The highway had been a viaduct, similar to both interstates 91 and 84 through Hartford, but over the past decade, a tunnel was bored beneath the existing route, and it’s set to open before the end of October of this year.www.daisylimo.com

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