Measuring Complexity of Built Environments : The impact of traffic lights and load of traffic levels on how drivers perceive stress

Abstract: To understand which factors affect the perception of stress while driving is interesting since it would help us to get closer to comprehending how the street network design can avoid putting stress on the drivers. Earlier research has measured drivers’ perception of safety under different street conditions by using video clips of real street environments. This study, that is carried out in cooperation with ITRL and it forms part of the MERGEN project, aims to introduce HCI techniques in order to prove that these techniques can bring valuable and credible results when substituting the conventional means of carrying out experiments. The study focuses on how the level of car traffic and the presence or not of traffic signs and lights affect how the drivers’ perceive stress emotion. To extract relevant information, a perceptual experiment was conducted in which 29 subjects were exposed to stimuli that represented four different virtual street scenarios. Each scenario comprised a unique case that combined the two factors under examination. In order to measure the levels of the perceived stress, the subjects of the experiment were asked to answer questions on how they perceive the following four aspects: confidence, comfort, route information and manageability of traffic load. It was concluded that the presence of traffic signs and automated traffic lights has a big impact on every aspect that was examined since a significant difference on the responses given was measured. It was also concluded that the level of car traffic does not play a very significant role when it alters in street scenarios where traffic signs and traffic lights are present. Nevertheless, the level of car traffic becomes a factor on how drivers perceive stress when the street scenario does not include presence of traffic signs and lights. The use of HCI techniques with the goal to extract information on how drivers perceive emotions managed to give back descriptive results, something that can enhance the use of this kind of methods in the evaluation of not only street network designs but any Built Environment design in general. The study is conducted using virtual scenarios but is meant to help better understand emotions in real situations.