The use of shared light, low-occupancy vehicles like bicycles and electric scooters (or e-scooters) is growing steadily in the United States and has become an essential part of urban transportation networks. Only 321,000 trips were recorded in 2010, rising to 112 million in 2021. These “micromobility” vehicles are typically designed to travel distances that are too short for driving but too far to walk. Almost 60 percent of all car trips in 2017 were less than six miles, which demonstrates the need for such micromobility solutions.

The rental of dockless e-scooter systems, in particular, emerged that same year and was operating in 65 cities in less than 12 months. Ride-sharing companies like Bird, Lime, and Superpedestrian make fleets of e-scooter available for users to rent for short periods through their respective apps. Because e-scooters have no tailpipe emissions and can replace short car trips, they are often the more eco-friendly mode of transportation. However, e-scooters still have environmental impacts that must be considered.

The sustainability of e-scooters

Giovanni Circella, director of the 3 Revolutions Future Mobility Program at the University of California, Davis, says that the use of e-scooters in US cities “tend to have somewhat positive effects in terms of environmental sustainability” by replacing the use of more polluting modes of transportation such as private cars and ride-hailing vehicles like Uber and Lyft.

In 2018, the Portland Bureau of Transportation launched a four-month pilot program to assess how e-scooters can help the city’s transportation needs. Data revealed that 34 percent of Portland riders and 48 percent of visitors took an e-scooter instead of driving a personal vehicle or taking an Uber, Lyft, or a taxi. 

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E-scooters can also promote a culture of active travel and “get the critical mass to justify investments in bike lanes and other infrastructure projects that support the use of active travel modes,” says Circella. However, shared e-scooters have mixed impacts, and they can also replace trips that would have otherwise been made by walking, bicycling, or taking public transportation, he adds.

Although the pilot program revealed that a number of users replaced motor vehicle travel with e-scooter sharing, “it also found that scooter-sharing replaced some lower emission active transportation trips,” says Susan Shaheen, co-director of Transportation Sustainability Research Center at the University of California, Berkeley.

Data shows that about 42 percent of Portlanders would have taken lower-emission trips if scooters weren’t an option: 37 percent said they would walk and 5 percent would’ve taken a bicycle. Moreover, the operations of the program—which involves the deployment and retrieval of e-scooters every day—likely added motor vehicle trips to the transportation system, but it is beyond the scope of the study.

It’s important to understand the overall impact of e-scooters beyond the trips they replace and consider other factors like manufacturing and longevity because results can vary based on the assumptions and scenarios modeled, says Shaheen.

A study presented at the 2020 IEEE European Technology and Engineering Management Summit analyzed the environmental impacts of e-scooters under different scenarios, changing different variables like the lifespan, kind of batteries, type of vehicle used to collect them, the average distance per lifetime, and more.

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In the best case scenario, where e-scooters last 24 months and have a swappable battery that is replaced by riding in electric vans, e-scooter sharing has a lower environmental impact than private cars, electric mopeds, and public transport busses, but is still less sustainable than trams, bicycles, and electric bicycles. However, in the worst-case scenario where the lifespan of e-scooters is only six months, they would have the worst environmental impact out of all. 

A 2019 study published in Environmental Research Letters also reported that ensuring e-scooters are used for two years decreases the average life cycle emissions significantly.

Overall, shared e-scooters are most sustainable when they are replacing personalized individual transport, but it’s possible that they are also catalyzing trips that would not otherwise take place, says Parth Vaishnav, assistant professor of sustainable systems at the University of Michigan School for Environment and Sustainability. Therefore, local governments should think carefully about encouraging e-scooter use, where to deploy them, and whether there are more effective ways of providing mobility, he adds.

How to make shared e-scooter systems more sustainable

E-scooters are a relatively sustainable mode of transportation, but they can become even greener. Shaheen says the public and private sectors can support e-scooter sharing systems by establishing solar docking stations where practical, using clean or renewable energy sources to charge e-scooters, and using electric vehicles to help with the distribution of scooters would be beneficial.

Switching to electric vehicles for the rebalancing and charging of e-scooters and opting for renewable energy has the potential to reduce the amount of fossil fuel involved in its lifecycle and operations. Most e-scooter companies have yet to explore these options. In 2019, Spin ran a 60-day pilot program and deployed dozens of solar-powered docking stations in Washington D.C. and Ann Arbor, but it’s unclear what the results were.

“The use of pricing and incentives to impact pick-up and drop-off behavior could also help reduce the need to rebalance the scooter network,” says Shaheen. This goes along with the recommendation of the aforementioned 2019 study to reduce collection and distribution distance to minimize the environmental impacts of e-scooters. It also suggests using more efficient vehicles, increasing scooter lifetimes, and charging less frequently. 

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Policies may also help reduce the environmental burdens of integrating e-scooters into the transportation system. For instance, allowing e-scooters to remain in public areas overnight can already minimize the trips required to pick up fully charged e-scooters. E-scooter misuse and mistreatment also reduce their lifespans, so implementing policies against these acts would be beneficial. Vaishnav recommends demanding suppliers to produce more durable scooters.

In general, shared dockless e-scooter systems do increase mobility in cities for a number of people and have the potential to reduce emissions in the transportation industry. Concrete steps like ensuring a longer lifespan, switching to renewable energy for charging, and using electric vehicles to pick up and drop off e-scooters would help make them even more sustainable.