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  • Microscopic Road Safety Comparison Between Canadian and Swedish Roundabout Driver Behaviour


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    While the broad concepts behind road design and signalisation are universally recognized for the sake of road user mobility between regions of the world—e.g. to accommodate visitors—specifics of intersection design philosophy and signalisation differ significantly between North America and Europe. This is not surprising given that the United States and Canada are not signatories of either the 1949 Geneva Protocol on Road Signs and Signals or the 1968 Vienna Convention on Road Signs and Signals which codify road signalisation throughout nearly all of Europe and much of Asia. Instead, intersection design in the United States and Canada, and much of the Pacific, is based off of the 1935 Manual on Uniform Traffic Control Devices.

    Design differences are especially striking regarding traffic control at intersections without traffic lights. While European design tends to favour a limited use of stop signs in favour of yield signs, or no signalisation at all, North American design favours two- and four-way stop signs almost exclusively. In fact, in general, yield signs in North America are used exclusively for slip lanes or merges, and never to control square intersections directly. Given the yielding nature of the roundabout design, it is unsurprising to learn that roundabout adoption has been very slow in North America. While roundabouts are a relatively new phenomenon in North America, they have existed in the United Kingdom since 1966 where the modern design of the roundabout was first conceived (at the Transport Research Laboratory).

    However, roundabouts are beginning to flourish across North America, against the prevailing stop-sign-predominant intersection design philosophy. Thus, studying this discrepancy in road design philosophy and resulting road safety record is especially relevant today given that many North American road users may not be familiar with unsignalised intersection design that the roundabouts introduce and this has been sighted as short and medium-term issue to overcome with further implementation of roundabouts in North America (e.g. Retting et al., 2007). To this end, there exists a need to study any differences in driving culture between the two continents, whether that difference is induced, or latent. In this work, an international, microscopic comparison of road user behaviour between a sample of road users selected from North America (specifically Québec) and from Europe (specifically Sweden) is performed using surrogate safety methods. Studying driver behaviour at roundabouts between these two regions is particularly relevant given that both regions share several climatic, environmental, demographic, and level of development similarities, and that, unlike many other types of road designs, roundabouts in North America have been directly transplanted from the first European designs (NHCRP 2010) and in practice are functionaly similar.

    The choice of using surrogate safety methods for this analysis was made to solve several issues related with historical accident data collection and comparison between jurisdictions, and, furthermore, offers much greater insight into road user behaviour and collision mechanisms (Tarko et al., 2009).

    While many international studies of road safety and design have been conducted, to date, only a limited number of international behavioural comparison studies have been attempted, and none have been conducted at the level of detail, and scale as in this study. This paper briefly reviews the literature and methodology to be used before presenting an exploratory analysis and regression analysis of speed, time-to-collision, and yielding post-encroachment time across twenty Québec and Swedish merging zones carefully selected to be similar in geometric design and environment.

    Literature Review

    Regional Effects

    As highly-developped countries, Canada, and Sweden especially, are among some of the safest countries in the world for motorists, cyclists, and pedestrians. Despite this, annual traffic fatality rates in Canada are nearly twice as high than in Sweden, as measured per 100,000 inhabitants (World Health Organization, 2013; OECD et al., 2015)), per 10,000 registered motor vehicles (OECD et al., 2015), and per billion veh-km travelled (OECD et al., 2015), and this despite a relatively comparable car occupancy and mode share (OECD et al., 2015). Figures of reported accidents per 100,000 inhabitants share a similar trend (OECD, 2015). These numbers are summarised in Table \ref{tab:se_accident_stats_summary}. While all of these rates have been observed to be decreasing consistently over the last 40 years, the proportion between the two countries has been fairly constant (OECD, 2015). Furthermore, fatality and accident rates in Québec are consistent with, and thus representative of the Canadian national average (Transport Canada, 2015).


    Statistic Canada Sweden Ratio Year Source
    Fatalities per 100,000 inhabitants 6.8 3.0 2.26 2010 (World Health Organization, 2013)
    Fatalities per 100,000 inhabitants 5.5 2.7 2.03 2013 (OECD et al., 2015)
    Fatalities per 10,000 registered motor vehicles 0.85 0.45 1.88 2013 (OECD et al., 2015)
    Fatalities per billion veh-km travelled 5.6 3.4 1.65 2013 (OECD et al., 2015)
    Accidents per 100,000 inhabitants 501.0 209.8 2.39 2013 (OECD, 2015)

    The disparity in road safety between Sweden and Québec is unexplained given that both share similar population sizes and density, levels of urbanisation (81 % in Québec versus 86 % in Sweden), climate, and economic development factors. The disparity might instead be explained by one of two sets of microscopic factors: road design, and road user behaviour and road culture. To this end, a comparative study of road user behaviour between the two regions is warranted by first isolating geometric factors as these are the most straightforward to control. One important difference is that cycling prevalence is significantly higher in Sweden than in Canada or Québec. On the other hand, roundabout design in Sweden tends to favour grade separated cycle crossings at many roundabouts (Sakshaug et al., 2010).


    Roundabouts might arguably be one of the best types of road infrastructure for direct comparison of road user behaviour and driving culture between North America and Europe. Although a relatively new phenomenon in North America (the first roundabout in Quebec dates back to 1998), roundabouts are one of the few types of road designs with near identical geometric and aesthetic design in both regions. This this is in large part due to the heavily European-influenced design of the roundabout in North American, e.g. roundabout design guides (as in NHCRP 2010) including Québec’s very own guide (Ministère des Transports du Québec, 2002).

    Key differences between the roudnabout designs are mostly-pedestrian and cyclist related, as Swedish sidewalks tend to incorporate cycle paths, even at intersections and roundabouts, but that these often bypass the roundabout entirely via grade-seperation (Sakshaug et al., 2010). In general, cyclist aversion to roundabout lanes might be attributed to higher accident rates and compounded by a lack of the safety-in-numbers effect (Daniels 2010).

    Road User Behaviour Comparison Studies

    While a number of studies have targeted specific types of road user behaviour present at roundabouts—most notably a study of gap acceptance of a saturated multi-lane roundabout in Lund performed by Irvenå and Randahl using some manually-annotated video data to calibrate microsimulation software (Irvenå et al., 2010)—very little research exists comparing tangible and objectively measurable difference in driving behaviour and driving culture between countries, especially after tightly controlling for geometric and land use factors. In part this is due to the challenge of coordinating such a study, and also in part due to the lack of a robust framework and technology for collecting and processing large amounts of driver behaviour. The bulk of international road safety comparison research seems to be concentrated on historical accident data (Morris 2011) or...

    The level of detail of such an analysis is made possible with improvements of large-scale automated surrogate safety an