<p>Every year many people all over the world are killed and severely injured in road traffic accidents. Even though driving too fast is a behaviour well known to contribute to both the number and the outcome of these accidents, drivers are still speeding. The general aim of this thesis, and its five empirical studies, is therefore to further the knowledge about drivers speeding behaviour by using the theory of planned behaviour and the model underpinning the driver behaviour questionnaire as frames of reference. The behavioural data used is obtained from field trials with intelligent speed adaptation and the speed reducing potential of this system is also examined. The results show that attitude towards exceeding the speed limits, subjective norm, perceived behavioural control and moral norm from the theory of planned behaviour, but also violations and inattention errors from the model underpinning the driver behaviour questionnaire, can be used to predict drivers’ everyday speeding behaviour. These two models can also be combined in order to gain further knowledge about the causes of speeding. Identification of drivers’ beliefs about exceeding the speed limits gives further insight into the underlying cognitive foundation of their attitude, subjective norm and perceived behavioural control. This provides valuable information for future design of speed reducing measures. Regarding intelligent speed adaptation, the results show that the ISA speed-warning device greatly reduces the amount of time drivers spend above the speed limits, and to some extent also reduces their mean speeds, but that this effect decreases with time. Although the drivers are not totally satisfied with the experience of the ISA speed-warning device, they like the idea and can see its usefulness. As the device tested is a first generation ISA speed-warning device, further research has the potential to greatly improve the system.</p>

Every year many people all over the world are killed and severely injured in road traffic accidents. Even though driving too fast is a behaviour well known to contribute to both the number and the outcome of these accidents, drivers are still speeding. The general aim of this thesis, and its five empirical studies, is therefore to further the knowledge about drivers speeding behaviour by using the theory of planned behaviour and the model underpinning the driver behaviour questionnaire as frames of reference. The behavioural data used is obtained from field trials with intelligent speed adaptation and the speed reducing potential of this system is also examined. The results show that attitude towards exceeding the speed limits, subjective norm, perceived behavioural control and moral norm from the theory of planned behaviour, but also violations and inattention errors from the model underpinning the driver behaviour questionnaire, can be used to predict drivers’ everyday speeding behaviour. These two models can also be combined in order to gain further knowledge about the causes of speeding. Identification of drivers’ beliefs about exceeding the speed limits gives further insight into the underlying cognitive foundation of their attitude, subjective norm and perceived behavioural control. This provides valuable information for future design of speed reducing measures. Regarding intelligent speed adaptation, the results show that the ISA speed-warning device greatly reduces the amount of time drivers spend above the speed limits, and to some extent also reduces their mean speeds, but that this effect decreases with time. Although the drivers are not totally satisfied with the experience of the ISA speed-warning device, they like the idea and can see its usefulness. As the device tested is a first generation ISA speed-warning device, further research has the potential to greatly improve the system.

Tidigare forskning har visat att bilförare tenderade att underskatta hastigheten de färdas i med ca 20%. Forskning har även visat att hastighetsupplevelse hos bilförare kan påverkas av ett utökat Field of View (FoV) vilket resulterar i lägre hastighetsval (Pretto et al., 2009; Schütz et al., 2015; Lidestam, Eriksson &amp; Eriksson, 2019). Utöver FoV har även virtuella vägmarkeringar (VRM), visats ha potentialen att påverka hastighetsval genom att bistå bilförare med ytterliggare visuell information kring dennes omgivning (Lidestam, Eriksson &amp; Eriksson, 2019). Attityder gentemot system som syftar till att påverka bilförares hastighetsval har studerats (Wall et al., 2013), med det finns luckor i forskning gällande hur dessa upplevs av bilförare med ADHD. Vidare har även upprepning av körningar med samma konstellationer av visuella stimuli har visats påverka hastighetsval vilket skulle tyda på perceptuell inlärning sker under bilkörning (Lindestam, Eriksson &amp; Eriksson, 2019). Syftet med den aktuella studien var att undersöka huruvida VRM påverkade hastighetsval samt hur de upplevs av bilförare med respektive utan ADHD. Studien ämnade att göra detta genom att besvara följande frågeställningar 1. a. Hur upplevdes VRM? b. Finns det en skillnad i upplevelsen av VRMs mellan bilförare med ADHD och utan ADHD? 2. Vilken effekt har ADHD, FoV, VRM och replikat på självvald hastighet? Resultaten visade att upplevelsen av VRM inte skiljde sig signifikant mellan de två guppen, trots detta skattades samtliga frågor kring upplevelsen av VRM högre av bilförare med ADHD än bilförare utan ADHD. Körningarna rapporterades som signifikant mer koncentrationskrävande av bilförare utan ADHD. Replikat och FoV uppvisade en signifikant interaktionseffekt på hastighetsval. Framtida forskning kan med fördel studera hur VRM kan utformas för att upplevas som mer hjälpsamma samt hur de bör implementeras för att bilförare ska vilja använda dem vid körningar. Det är viktigt att framtida forskning i området även inkluderar bilförare med ADHD för att säkerställa att system som utformas även är gynnsamma för dessa bilförare.