Association of Nighttime Speed Limits and Electric Scooter–Related Injuries

This cohort study investigates whether nighttime speed restrictions are associated with the incidence of electric scooter–related injuries in Finland.


Introduction
Electric scooters (e-scooters) are associated with a high risk of injuries, especially injuries occurring at nighttime or under the influence of substances. 1 Several nighttime restrictions have been attempted to decrease the number of injuries, but the outcomes of those restrictions have been evaluated only without the use of user data. 2,3In addition, only limited data have been reported about the user database incidences of e-scooter-related injuries. 4,5Hence, we aimed to examine whether nighttime speed restrictions are associated with the incidence of e-scooter-related injuries.

Methods
In this retrospective cohort study, we identified all the patients admitted to the emergency department of Tampere University Hospital (Tampere, Finland) between April 24, 2019, and September 30, 2022.The hospital is the only trauma center providing 24-hour emergency services for its catchment population of approximately 550 000 inhabitants.In addition, we requested user

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Open Access.
This is an open access article distributed under the terms of the CC-BY License.Hospital's research director approved the study and waived the need for informed consent due to the study's retrospective nature.We followed the STROBE reporting guideline.
In 2022, the nighttime speed restrictions were used in Tampere, as the maximum speed was electronically limited by the e-scooter companies to 15 km/hour between 12 AM and 6 AM.Hence, the summertime (June 1 to August 31) incidences were compared to evaluate the association of nighttime restrictions with incidence.
A search for e-scooter-related injuries was performed using related keywords to identify patients (eAppendix in Supplement 1).After identifying possible cases, electronic health records were examined manually for each of the patients.Injuries were categorized according to their location and severity.The severity was evaluated with the Abbreviated Injury Severity scale.
Incidences were calculated with Poisson distribution and reported with 95% CIs.All the analyses were performed using the epitools package from R version 4.0.1).

Discussion
To our knowledge, no previous study has examined the association between nighttime restrictions and the incidence of e-scooter-related injuries.A limitation of this cohort study is its retrospective nature, which could bias our results.However, we evaluated the association of nighttime restrictions with the user database incidence of e-scooter-related injuries.On the basis of our results, the nighttime speed limit was not associated with reduced injury incidence.The results from our study can be used as reference values to evaluate the efficacy of new interventions.Although e-scooterrelated nighttime injuries are a concern, it seems that the nightly speed limits might not be effective enough to substantially reduce them.

Table 1 .
Characteristics of Electric Scooter-Related Injuries, Stratified by Year a Because of Finnish legislation, frequencies less than 5 cannot be reported as exact values.

Table 2 .
Summertime Incidence of Electric Scooter-Related Injuries a a The summertime period was June 1 to August 31 during each of the study years.bNighttime (12 AM to 6 AM) speed restriction was set to 15 km/h in the summer of 2022.
3 (R Project for Statistical Computing) from December 2022 to January 2023.