Study: Estimating the emissions savings of shared e-scooters

Switching to e-scooters reduced greenhouse gas emissions by up to 45% and reduced travel time by 47% compared with trips replaced, data shows.

A study by University College London (UCL) researchers has found that in 2021, the adoption of e-scooters in Bristol reduced greenhouse gas emissions by up to 45% compared with the trips taken with transport modes that they replaced. The researchers also found e-scooters provided considerable congestion and time-saving benefits. 

Here we take a closer look at the study and its findings.

Measuring emission and congestion savings

This latest study by researchers from the Energy Institute at UCL is one of the first academic studies into e-scooter use that incorporates a first-hand environmental assessment of the service, uses real-world trip data and takes into account emissions created from the factory floor to end-of-life for e-scooters.

Using raw data from e-scooter trials run by Voi, the study analysed over 190,000 e-scooter trips to investigate the mode shift impact in Bristol over a three-month period in 2021.

To measure modal shift, Voi users were asked which mode of transport each e-scooter trip replaced after the ride via an in-app survey. This is the first study to include granular trip-level data on modal shift. 

To estimate the environmental impact, the researchers conducted a full Life Cycle Assessment (LCA) of the service using updated available figures, rather than relying on global averages as previous studies have done. 

The researchers used raw data from Voi’s suppliers, operations, fleet utilisation and end-of-life practices combined with emission factors from the literature and environmental databases. To compare trips with alternative modes, UCL used the conversion factors as published by the International Transport Forum (Cazzola & Crist, 2020).

Using Google API, the route of each trip and information about the mode replaced, researchers accurately simulated the replaced trips and estimated the time, distance and emissions of the replaced trips. Comparing this data to Voi’s trip data, they accurately measured the distance, time and emission savings of each trip conducted via e-scooters. The emissions impact we’re calculated by finding the difference between the emissions from e-scooter trips and the emissions from its new or replaced trip.  

The LCA results revealed vehicle lifespan and operations greatly impact service emissions, demonstrating that the efficiency of e-scooter providers’ operations is key to reducing emissions.

47% reduction in travel time and up to 45% trip emissions cut

According to data collected, 37% of the examined e-scooter trips would previously have been taken on foot, 19% by car, 14% by bus, 10% by cycling, 2% by another transport mode and 2% by motorbike.

Looking at the sample trips taken from Bristol over a three-month period, e-scooter trips replaced over 48,000 kilometres of motorised transport journeys, helping to reduce pollution and congestion.

The chart below shows the e-scooters’ greenhouse gas emissions compared with each type of replaced transport based on a long-lifespan e-scooter with low operational impact. 

The study also found that e-scooters drastically cut commuting times, especially during peak hours, helping to save users a total of 4,000 hours during the course of the study, equivalent to a 47% reduction in median travel time per trip.

High vehicle utilisation and sustainable operations are key for emission reduction

The researchers estimated the overall impact of introducing e-scooter services under different scenarios for vehicle lifespan and emissions related to operations. Overall, the scenario with long km lifespan and average operations most closely resembles Voi’s set-up in Bristol and other cities. Considering this LCA scenario, the studied trips resulted in a carbon emission reduction of 45.8%.

The findings highlight the importance of vehicle lifespan and operational efficiency to ensure — and increase — the environmental benefits of shared e-scooters.

Since 2018, Voi has invested in extending vehicle lifespan and ensuring high utilisation of its vehicles. In Bristol and other ‘high utilisation’ cities, scooter lifespan can even reach up to 18,000 km over a period of 5–7 years. 

In many cities, Voi is a top-performer in terms of utilisation (measured by trips per vehicle per day). Voi has also invested in efficient operations, thanks to route optimisation, task coupling and in-field repairs as well as transitioning to electric vans and cargo bikes. 

However, in cases of short vehicle lifespan or less efficient operations, the emissions savings quickly diminish and can even contribute to added trip emissions.

Learnings for cities and policy makers

These findings show that cities and regulators should encourage and select operators that have proven programmes to ensure the sustainability of their fleet and their operations. 

The study’s author, Emmanouil Chaniotakis, comments: “Essentially, the findings suggest that shared e-scooters have the potential to provide significant benefits in terms of mode shift, congestion, time savings and emissions reduction if implemented effectively. By replacing trips previously taken by other modes of transportation, shared e-scooters can reduce emissions and congestion during peak periods.”

“Given the sample of trips is from 2021, the early days of the service in Bristol, it’s likely the environmental benefits have increased since as the service has become safer and more reliable”, says Emmanouil Chaniotakis. 

Who ran the study?

Commissioned by shared e-scooter company Voi, the independent study by researchers from the Energy Institute at UCL is one of the first academic studies into e-scooter use that incorporates a first-hand environmental assessment of the service and uses real world trip data.

You can see the full study here.

More information about Voi’s commitment to sustainability can be found at www.voi.com/sustainability/