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The objective of this research is to investigate latent differences in road user behaviour and experience that may explain differences in accident history beyond any road safety effects derived from road design and traffic composition. To that aim, a number of roundabouts in Québec and Sweden are selected on the basis of similarity in design, for cross-sectional comparison. The modern roundabout is chosen as a case study as its implementation in North America is identical to that of Europe (where the design originated), and because roundabout operation relies heavily on road user behaviour (right-of-way is performed exclusively through rules of priority). This approach to intersection control is in stark contrast with typical stop-sign and traffic light control used throughout North America. Analysis of behaviour and resulting safety is performed proactively using automated computer-vision-based trajectory extraction of road users from video data, coupled with surrogate safety methods. Surrogate safety measures of interest for this study include speed and time-to-collision, modeled using motion-pattern motion-prediction.  Accident records recorded at the sample of roundabouts studied are found to be consistent with national averages of each country respectively (twice as high and severe in Québec as in Sweden). After controlling for various geometric design features, land use, construction year, traffic exposure, and traffic patterns, an overall tendency of lower speeds and fewer serious conflicts (as measured by time-to-collision) are found at the Swedish roundabouts. These resultsare found to be consistent with local and national accident records, and  would suggest that some important latent regional factors---possibly related to driver education, culture or traffic safety enforcement---are at play at the microscopic level.Further investigation of these regional factors is warranted in future road safety studies.