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We are pleased to share that Siobhan O’Connell and Steven Mairs have had their article “Pedal Cycle Investigation: Using GPS and Activity Data to Reconstruct Road Collisions,” published in the latest edition of the Expert Witness Journal.
The article examines the growing role of digital activity data in road traffic collision investigations involving cyclists. As the use of GPS cycle computers, wearable technology and fitness platforms such as Strava continues to increase, these devices are becoming an increasingly important source of information for investigators seeking to understand a rider’s movements, speed, positioning and activity before and after a collision.
A key message of the article is that not all GPS data should be treated equally. While platforms such as Strava provide accessible visualisations of cycling activities, the authors explain that the information shown online is often processed, recalculated or smoothed, meaning it may not accurately reflect the original data recorded by the device. This distinction is particularly important when investigating critical events such as sudden braking, acceleration or interruptions in recording.
The article outlines three distinct tiers of GPS-related evidence:
- FIT files – the original activity files recorded by the device, providing the highest-quality data for forensic analysis, including timestamps, speeds, distances and sensor information.
- GPX exports – useful for analysing routes and movement, but typically containing reduced datasets that may require further calculation.
- Website activity displays – the lowest evidential tier, as they present interpreted versions of the data rather than the original recordings.
To demonstrate the importance of using original source data, the article includes a case study of a collision involving a cyclist in a road race. The investigation revealed that while the original FIT file contained gaps in the recording around the time of the collision, the corresponding Strava activity displayed a continuous speed trace by effectively filling in the missing data. The example highlights how reliance on processed platform data could potentially lead to inaccurate conclusions.
Siobhan and Steven also discuss the limitations of GPS devices, noting that they are not designed as collision recorders and may be affected by factors such as low sampling rates and positional inaccuracies. However, when considered alongside physical evidence, scene examination findings and witness accounts, GPS data can provide valuable additional insight for collision reconstruction experts.
They conclude that, wherever possible, investigators should obtain and analyse the original FIT file to ensure the most accurate and transparent assessment of the evidence. As GPS and activity-tracking data become increasingly relevant in litigation and insurance investigations, understanding the strengths and limitations of different data sources is essential.
The full article can be found on page 54 of The Expert Witness Journal
