E-bike deaths and injuries are on the rise

In London, UK, last month, Sakine Cihan was hit by an e-bike and later died in hospital. This tragic incident is not the only one. E-bikes have been implicated in fatalities in studies conducted in the Netherlands, Israel and Beijing, although almost all of these fatalities were due to cyclists and not pedestrians. Studies in Israel and Switzerland have found more injuries, again almost entirely among e-bike users, not others.

Post-collision e-bike, courtesy ABC6, Philadelphia

Perhaps that’s what the New York administration was thinking in October 2017 when it cracked down on e-bikes, especially for delivery services. At the time, he claimed he had strong data supporting increased danger to pedestrians. However, when pressed later, a city spokesperson made it clear that they were not tracking e-bike incidents separately.

311 records persistent and “chronic” problems caused by bicycling, in-line skating or skating, but does not break down those complaints to show how many came from e-bikes, Grybauskas said. About 400 such calls have been made in the past year, most from the Upper West Side, Grybauskas said. But that number includes complaints about all kinds of bikes, as well as skateboarders and rollerbladers.

A year later, New York changed its position. Since July 2018, electric bikes limited to 20 km/h are authorized, in particular those whose acceleration is only controlled by pedaling.

So what are the real dangers of e-bikes, and for whom?

The answer varies somewhat around the world. In the Netherlands, the study shows that it is mostly older male cyclists who end up in hospital or worse. 31 of the 38 deaths in the study were men over 65. The study authors point to several factors that combine to cause problems. The increase in speed of e-bikes compared to pedal bikes in the same age bracket suggests that reduced reaction time combined with slower reaction times was a factor. The increased weight of the bikes combined with a decrease in muscle tone was seen as a concern. And that it was men and not women who constituted the overwhelming majority indicated a difference in risk perception, likely due to a sharp decrease in physical abilities of men compared to women.

In Israel, the study between 2013 and 2015 found 795 injured, 8% of them pedestrians, not drivers. Children, women and the elderly were relatively evenly represented among the injured. Two of the pedestrians who were subsequently struck died of their injuries. The study focused on poor cycling infrastructure, with both a lack of separate cycle lanes and pedestrians accidentally stepping on cycle lanes as cause for concern.

Switzerland has a long history of e-bike adoption, with increasing penetration from 2005 to the present day. And with that came injuries. The study in question tracked e-bike related injuries for people admitted to an emergency department in Bern. Again, more mature men make up the majority of those presenting with injuries, with 70% being male and most over 40 years old. This study did not show a decrease in physical abilities, but another common urban cycling challenge in European cities, trams. No pedestrians were reported among the injured.

Chinese studies have found yet another pattern of danger. Most injuries on e-bikes came from a lack of helmets and collisions with cars. The major study in Beijing was devoted to the interactions between the car and the electric bicycle.

The impact force of an electric bicycle and a cyclist on a pedestrian can be almost four times stronger

Some commonalities emerge from various studies and reports from around the world. The first is that e-bikes are both heavier and faster, making them more dangerous both for their riders and for pedestrians unlucky enough to be hit by them. This can be more clearly understood by looking at the impact energy formula:

F = (0.5 * m * v^2) ÷ d

Let’s separate that a bit. F is the force. M is the mass. V is the speed. D is the distance traveled between the moment of impact and complete stopping. There are two components that matter for this, mass and velocity. Electric bikes typically have two to three times the mass of non-electric bikes, and this extra mass adds to the rider’s body weight. Taking an example, a 70 kg cyclist on a 10 kg road bike has a combined mass of 80 kg, whereas if he is on a 30 kg e-bike the combined mass is 100 kg, or 25 % more than alone. E-bikes are generally legally limited to 25 km/h on city streets, while the average cycling speed in Copenhagen is 15.5 km/h. Assuming a 9.5 km/h higher impact potential and a 25% higher mass, the impact force of an e-bike and a cyclist on a pedestrian can be almost four times greater.

This potential for much harsher impacts on pedestrians understandably worries safety experts. Let’s take another example, that of a heavier and faster electric bicycle, both exist. The Sur Ron MX e-bike is top of the line and sold only for off-road use, although it’s easy to find videos of it on city streets. It weighs 50 kg and has a top speed of 80 km/h. A collision with a pedestrian with a cyclist of the same weight would be around 45 times harder.

Table of stopping distances courtesy of GSCE

By pulling on another wire, e-bikes cause more accidents among men than among women in Europe. The experience of the Netherlands is the most revealing. E-bikes are especially dominant among older people, as they no longer have the physical ability to ride a bike themselves due to failing health. However, e-bikes are also heavier and move faster than the bikes they used before. Again, physics does not favor this equation. There are three key points to respect. First, in general, human reaction times worsen with age, although this is both highly variable and somewhat trainable. If two cyclists see something ahead of them on the road, like a pothole, the older one will react a little slower by braking or swerving. The second is that with a higher speed on an e-bike, there is less time before reaching the obstacle. This combination alone is a challenge. But next is the kicker. As with impacts, braking is exponentially related to speed, not linear. This means that as you go faster it can take much longer to slow down, and most of the slowing down occurs at the end of the braking cycle, i.e. it takes much less time to slow down from 15 km/h to 0 km/h than from 25 km/h to 15 km/h. The weight of an e-bike has one final impact. They are a bit less nimble, in general, than lighter non-electric bikes. It takes more muscle and technique to do a swerve or a bunnyhop, one of which usually decreases with age.

Cycling infrastructure is important to consider, but it comes with its own set of issues. Separate cycle lanes shared by e-bikes mean that heavier and faster vehicles co-exist on narrow paths with relatively hard limits. Many cycling organizations have fought against allowing e-bikes and e-scooters on city bike lanes around the world.

Finally, e-bikes share something with electric cars: they are delightfully quiet. This too comes with a problem. The disparity in weight and speed means that pedestrians have to treat them more like motorized vehicles in terms of respect, but pedestrians don’t hear them coming.

City planners and road safety regulators are struggling to get a handle on e-bikes. They offer huge benefits for urban mobility, they reduce congestion, they offload overloaded public transport, each e-bike is arguably one less car on crowded city streets and they don’t pollute. But the interaction between e-bikes, pedestrians, cars, trucks and other cyclists requires special attention, especially as e-bikes continue to take market share from small motorcycles and bicycles.


 

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