Perception, change detection and utilisation of roads using dynamic information: a theoretical review

Dynamic speed limits are part of the latest traffic management pilot program in the Netherlands in order to adjust real-time driver speed to the circumstances of the road condition. The general objective of this literature review is to understand the effectiveness of dynamic speed limits in terms of perception, as little is yet known how people perceive changes in dynamic speed limits in relation to prevailing road conditions. Dynamic speed limits are displayed on information carriers with the intention to change the drivers’ speed. A number of previous studies on change detection, such as Rensink (2002a), have shown that ‘under a wide variety of conditions we can be amazingly blind to changes, failing to see them even when they are large, repeatedly made and anticipated’. This phenomenon has been reverted to in literature as change blindness (Rensink, 2002a). Dynamic speed limits displayed on information carriers compete with a wide variety of other types of information as previous studies have shown the human information-processing system is limited in its ability to deal with the amount of information displayed (Wickens et al., 2004). Dynamic speed limits are considered road information. They are intended to inform drivers about the status of the road and the goal is that drivers should adapt to them in real-time. In this paper a framework is suggested to help researchers distinguish between route information, road information, road user information and driving unrelated information. This literature review shows that information especially prone to change blindness, is information that lacks perceptible transient motion signals when changing (e.g. due to masking or gradual change), is not relevant for the task at hand, or violates expectations about objects of significance for performing the task at hand. Both transient motion signals attracting attention, as well as the task at hand, influence the visual search needed to build an internal representation of the environment. Based on the current literature review, it can be concluded that detection of changes in dynamic speed limits will suffer from gap-contingency masking and changes in semantic identity. It remains unclear whether repetition of successive information carriers will reduce the chance of detection of changes in dynamic speed limits. Detection of these changes might be increased as they are necessary to maintain an appropriate speed; this is part of the driving task. In conclusion, some drivers will not detect changes in dynamic speed limits, but it remains unclear to what extent this will be the case. Subsequent research should establish the extent of the change blindness effect and whether it can be reduced to increase situation awareness and the effects of dynamic traffic management