A multi-method approach to explore risk factors in truck-bicycle encounters

Abstract

Currently, the numbers of cyclists are increasing in many cities worldwide. People are encouraged and motivated to cycle, as it improves their health, reduces the negative effect of car traffic and creates more liveable and vibrant cities. At the same time, current economic development, customers’ requirements and shippers’ strategies are contributing to the growth of truck traffic in urban areas. Trucks and cyclists must share the constrained urban space, and their routes often overlap. Experiencing an accident with a truck presents one of the most serious encounters imaginable for a cyclist, and just the presence of trucks on the roads may deter some people from cycling. Therefore, finding more out about safety between trucks and cyclists has been recently recognised as an important topic requiring extensive research. To get more comprehensive knowledge about the topic, several methods have been applied within a Norwegian context in this PhD project. These methods included the literature review, analysis of accident records from the national database and review of in-depth investigation reports of fatal accidents, nationwide survey of cyclists regarding their conflicts with trucks, faceto- face interviews with trucking industry employees and behavioural and conflict analysis using long-term video recordings of traffic on several sites. In particular, the infrastructure-related risk factors were of research interest. Most truck-bicycle encounters occur in urban areas; thus, focus has been directed towards urban environments. Trucks over 3.5 tonnes (excluding vans) have been considered in this research. The main conclusions from each method are summarised below. The literature review found that the current understanding of truck-bicycle safety is based on accident analysis, and that particularly technological tools to detect the cyclists in the trucks’ blind spots are in the centre of research attention. Accidents between trucks and cyclists (particularly involving right turning trucks) have been recognised as severe road safety problem in urban areas since 1990’s. They are not frequent, but typically have very severe consequences for involved cyclists. Additionally, several knowledge gaps were identified within the review, such the lack of an explanation for the overrepresentation of female cyclists in accidents with trucks, lack of effort to identify risk factors from higher levels of the transport system or lack of safety analysis of less severe encounters in traffic (e.g. conflicts). The analysis of the accident records from police databases revealed that the percentage of cyclists killed in accidents with trucks among all cyclists’ fatalities in Norway is one of the highest in Europe. Residential areas were the most frequent environment for truck-bicycle accidents, with intersections and crossings being the most common locations. Right-turning accidents were recorded as those that happened most often. In addition, female cyclists were found to be overrepresented in serious and fatal accidents with trucks. The review of the in-depth investigation reports of fatal truck-bicycle accidents clarified the characteristics of the truck drivers and their vehicles involved in the accidents with bicycles. Most of the trucks were relatively modern, having the required safety equipment and being driven by experienced drivers. Moreover, the review provided deeper insight into the development of the accidents themselves. The combination of various risk factors was found to contribute to each accident’s occurrence. The nationwide questionnaire survey of cyclists identified recurring types of conflicts with trucks. Over 60% of respondents reported at least one conflict with a truck over the past 12 months. Surprisingly, overtaking conflicts were reported as being the most frequent. It appears that the distribution of conflict types is significantly different within Norwegian cities, a finding which might be partially explained by the cities’ different infrastructure layouts. The face-to-face interviews with truck drivers and managers from the companies operating their trucks in Trondheim provided valuable information about the risky locations existing in that city. Furthermore, the route planning procedures within the companies were discussed, and it was found that cyclists’ needs are not considered during route planning. The long-term video recordings of eight sites in Trondheim provided unique data about truckbicycle encounters and behaviour in actual traffic situations. In total, during 619 hours of observations, there were 993 encounters recorded, 34 of them resulted in a conflict defined by an evasive action. Encounters between right-turning trucks and straight riding cyclists were evaluated as most risky, and several examples of risk awareness behavioural patterns were observed. The applied multi-method strengthened the benefits and reduced the shortcomings of each method. It enabled the exploration of the truck-bicycle safety phenomenon from different perspectives and therefore provided a more comprehensive overview about the research topic. Each method identified different risk factors from different levels of road transport system. The knowledge of risk factors was further applied on evaluation of the common cycle infrastructure layouts.