The Adverse Effects of Paradigm and Pragmatism on Road Safety With Case Studies in Traffic Conflicts Technique and Cyclist Safety at Roundabouts

Abstract

This thesis takes a multi-disciplinary approach to the hypothesis that “Engineering paradigm and pragmatism are having an adverse influence on road safety.” This proposition has been examined through a wide-ranging qualitative literature review, a systematic quantitative literature review and a survey of Australian road authorities. These provide evidence and reasons for adverse effects, drawing from both social science and engineering perspectives. The hypothesis was then tested using two known problems in road safety and a proof by contradiction methodology. If rejecting accepted paradigm (case study 1) and pragmatic practice (case study 2) lead to significant new knowledge being found, then current paradigm and pragmatism are forming a barrier to optimal road safety research. The paradigmatic case study considers Traffic Conflict Techniques (TCT), which theorises that crash risk assessment can be determined based on observations of normal traffic events. While TCT is used for problem diagnosis, numerous conceptual and practical difficulties prevent a Holy Grail for safety practitioners being realized: TCT cannot predict crash risk independently of a crash record. The case study considers this problem by rejecting the TCT paradigm and developing a new theoretical framework based on Extreme Value mathematical theory – the only proven basis for predicting rare events from observations of more common events. The method developed by this theoretical case study, labelled Traffic Events Theory (TET), overcomes all known problems associated with TCT. In particular, TET is mathematically complete and should therefore enable risk assessment to be undertaken without recourse to a crash record. The pragmatic case study involves cyclist safety at roundabouts, and whether radial roundabouts are safer than tangential roundabouts. This has been theorised but cannot be shown using the pragmatic approach of associating crash data with geometric design features due to the inherent complexity of roundabouts. The pragmatic case study rejects the pragmatic approach in favour of an observational method applied to a tangential roundabout converted to a radial design. This has identified geometrically-related implications for motion detection in peripheral vision. In particular, the case study identified that tangential geometry created conditions under which an approaching driver could not physically detect a cyclist, exacerbated negative associations between cyclist tracking and safety, and made more likely situations where a circulating car will briefly hide a cyclist from an approaching driver. These are all effects that have not been identified using the type of statistical safety studies that traffic engineers use for pragmatic reasons. The case study results represent valuable contributions to road safety knowledge. They also confirm, under a proof by contradiction approach, that “Engineering paradigm and pragmatism are having an adverse influence on road safety.” That is, adverse effects on road safety are systemically-based with anecdotal case studies presented by other researchers not merely troubling incidents occurring in isolation. But if this hypothesis seems critical of traffic engineering and the road safety field, it also offers practitioners the opportunity to reinvigorate their profession into the dynamic, politically-aware and socially-engaged practice that characterised the golden age of engineering.