A psychological perspective of drivers’ speed preferences in work zones and its implications for policy and practice

Abstract

All traffic safety work conducted in Norway is based on the goal that nobody should be killed or severely injured in a traffic crash. According to this philosophy, called “Vision Zero”, road authorities will work proactively to improve traffic safety. This viewpoint should also be applicable to work zones. In Norway, in the period 2005–2009, 23 traffic deaths related to work zones were registered. The causes pointed to by the traffic accident analysis performed by the Norwegian Public Roads Administration (NPRA) demonstrated that several of those traffic crashes involved local conditions and organisational factors, such as lack of warning/safety measures and inadequate interactions between contractors and road authorities. Even though these factors were recognised as being partially accountable for the crashes, the underlying human factors did not receive an in-depth investigation. In recent years, several field studies have been performed to assess the effects of a varied number of traffic control devices (e.g. traffic signs, road markings, etc.) on driving behaviour in work zones. Nevertheless, only a few studies have addressed the effects of those countermeasures from a behavioural and psychological perspective. For this reason, the main aim of this thesis was to increase our understandings of the role of human factors in roadworks safety, more specifically, the effects of drivers’ personal variables and their interactions with the traffic environment on speed preferences in work zones. In the first paper, a video-based experiment was developed to examine the effects of roadwork activity on preferred speeds. The results corroborated other studies that indicated that drivers prefer lower speeds if they see a reason for it (i.e. visible work activity). Analysis of the drivers’ self-assessments of the elements that influenced their speed choice in work zones showed that speed regulations and transient motives were the factors that gave significant contributions to predicting speed preferences. The results from the first paper allowed us to establish the importance of the road characteristics and surroundings when drivers choose which speed they would prefer in work zones. In the second paper, we analysed drivers’ personal characteristics in terms of personality traits, attitudes, risk perceptions, and driving styles and their impacts on drivers’ preferred speeds at work zones. An important contribution of this paper is in recognising the interaction and indirect effects of personality traits on speed preferences in work zones. The indirect effects of personality traits were found to be through attitudes, risk perceptions, and driving styles. Furthermore, it was found that the situational cues (i.e. visible work activity) influenced the expression of personality traits. This perspective has not been widely investigated before. Roadwork activity was found to act as a moderator in the relationship between personality and preferred speeds, where visible work activity influenced the strength and direction of this influence. The results give recommendations for future studies and highlight the importance of taking into consideration specific traffic situations that can be of great importance when studying personality traits and their effects on driving behaviour. The third paper utilised another approach to investigate the effects of drivers’ personal characteristics on speed preferences in work zones. It strengthened the assumption that the situational cues are important variables to consider when explaining driving behaviour. For instance, situational cues (such as roadside delineators) that indicate that a road section is not in typical condition gave greater reduction in preferred speeds. We could also conclude that for some drivers scoring higher on specific personality traits the situational cues should be stronger in order to indicate what kind of behaviour is expected for the situation. For the study in this paper, we utilised a series of screenshots of one work zone at the point after passing the reduced speed limit sign. The scenes with stronger situational cues yielded preferred speeds closer to the posted speed limit. In contrast, for the scenes that appeared to have weak situational cues (e.g. the road seems in good condition), drivers preferred higher speeds. We also found that preferred speeds increased with age, higher scores on the normlessness scale, and higher self-assessment of one’s driving skills. Recommendations to road authorities were given based on the findings. Overall, the present thesis makes significant contributions in understanding speed preferences in work zones. First, it provides evidence that situational factors are of great importance for drivers when choosing at which speed they prefer to drive in a situation. The results provide support for road authorities when it comes to the importance of using countermeasures that emphasise to drivers that the road section is a work zone. Second, the results point to the fact that even though drivers’ personal characteristics are important factors that influence driving behaviour, the environment will facilitate certain personality expressions that manifest in the form of risky behaviours. It is important to keep in mind that situational cues indicating a situation (in this case work zones) that give guidance for the expected behaviour have the possibility to inhibit the expression of certain personality traits in the form of risky behaviour (e.g. higher speeds). Moreover, this thesis also contributes by gathering the existing knowledge from reports and articles about drivers’ behaviours in work zones and discussing it from a psychological perspective. The knowledge produced by this thesis is expected to provide a stronger basis for policy and traffic management practices in work zones and to enhance traffic safety for both drivers and road workers.