E-scooter design makes crashing easy
The unstable design of e-scooters makes them easier to crash, and with a higher chance of serious injury, says an AUT mechanical engineering researcher.
Since e-scooters took off in recent years, there have been numerous reports of injuries and several deaths associated with their use.
Dr Milan Paudel, an AUT lecturer with a PhD in mechanical engineering, has conducted several studies into the design of e-scooters and how they crash.
He told 1News recently that a combination of unstable design, fast speed, careless operation and the nature of urban environments can make riding e-scooters a risky business.
The design of e-scooters makes them "unstable" and more dangerous when operated incorrectly. Compared to bicycles, e-scooters are harder to control with one hand, require more effort to balance, and are prone to "external disturbances".
Small wheels, short wheelbase, and high centre of gravity when a rider is standing are some of the factors behind these vulnerabilities.
"Riders constantly have to provide some kind of control, either by moving their body left and right, or continuously adjusting the steering to maintain the balance," Paudel said.
Because they're regularly used on footpaths, scooters often share the same space as pedestrians. But pedestrians only account for around 10% of e-scooter-related injuries.
Paudel said 60% of crashes were isolated accidents. This is because e-scooters' small wheels mean riders can "easily get thrown off" when they encounter obstacles on the footpath or road.
"Maybe they encounter potholes, maybe they encounter loose pebbles on the ground. They can easily be destabilised, and their steering can become very chaotic."
Because some scooters do not have indicator lights, riders may have to use hand signals to let others know which way they're going, making balance tricky.
Scooters also travel faster than pedestrians, creating more conflicts and risky scenarios.
New road rules set to take effect at the end of this year will allow people on e-scooters to ride in cycle lanes. "The cycling path seems to be much smoother, which may be beneficial for these scooterists," Paudel said.
According to his research, e-scooter riders have a higher probability of suffering a severe head injury in a crash than those on bicycles. He found there was a 30% to 50% chance of a severe head injury when travelling between 10 and 12km/h – this sharply increased to 91% past 15km/h.
Paudel said e-scooters' design changes the way riders fall to the ground after a sudden stop. They have two points of contact – the deck where the rider stands, and the handlebars – which sit lower than those on bikes.
"It has little effect when it crashes to prevent forward motion," Paudel said. "You do not have anything in between to dampen that motion, to cushion that motion. So, simply, you will slam on the road."
Bikes, on the other hand, have three points of contact, with the driver sitting, creating friction that weakens the momentum of a crash. Head injuries however, are still common after bike crashes.
When high speeds come into play, the effects of a crash get worse, as more speed means more energy pushing the rider forward.
"Although the energy might be the same, the speed at which you are likely to hit the ground is much higher in the case of a scooter compared to a bicycle," Paudel said.
In New Zealand, scooters must have a maximum combined power output of 300W, and in many areas, companies limit the speed at which they can travel.
There was a "grey area" here, Paudel said, saying he has seen "many" scooters whizz past at 40 to 45km/h. He said it is easy to modify motors to exceed this output and models over 300W are available online.
The best way to reduce the risk of serious injuries was to simply wear a helmet, although an Auckland Transport study found only 11% of shared device users and 44% of private device users wore helmets.
Paudel said it was "essential that we start changing our behaviour".
It was also a good idea to use scooters as intended by not riding with two people, as it made the devices harder to control. "It increases the chance of injuries because not only is there a person at the front, but a person at the back," Paudel said. "The front person is impacting the ground. At the same time, there is a person behind who also has a tendency to land on top."
He also said the effects of alcohol impairment - including delayed reaction time, a lack of postural stability and reduced risk averseness - made scooters harder to control.
"Sometimes it may encourage you to go faster, make abrupt steering motions, and weave in and out of crowds. It encourages risky behaviour at the same time; when you are intoxicated, you lose the ability to balance the scooter."
For riders, Paudel recommended wearing a helmet, using scooters that have a seat, and keeping up with regular maintenance if they own one. "Not only changing the batteries but also the routine inspection, especially for the air brakes and whether the tyres are worn out."
He said it was good to see shared scooters in Auckland, such as Lime and Flamingo, come with helmets, but wanted the law to go further. "Making it mandatory rather than recommended could have increased the percentage of helmet use."
While scooters now have better suspension, providers could go further by increasing the number of seated models. "It's why the bicycles seem to feel much safer than the e-scooters."
Education around scooter safety is also something that could help reduce crashes, as a large number of those claiming ACC are aged between 15 and 30. Paudel said this could be done in schools.
"We have to make them aware. What happens when you are riding an e-scooter and not paying much attention. When you crash, what happens to your body. What kind of injuries you may sustain. All these things could lead to better riding behaviour."
Useful links
- Evaluating the safety of small-wheeled micro-mobility devices: A design-agnostic, performance-based experimental approach - ScienceDirect
- Milan Paudel | Mōku | About | Auckland University of Technology
- 'Simply, you will slam on the road': How dangerous are e-scooters?
- Mechanical Engineering Honours Degree - AUT
- Mechanical Engineering Major - Bachelor of Engineering Technology - AUT
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