Dynamics of Drivers’ Trust in Warning Systems

This paper focuses on how the behavior of drivers in response to warning systems is influenced by their trust in those warning systems. The experimental examinations show that a) false alarms result in a reduction in trust and an increased reaction time to braking, b) a lack of alarms result in a delay in the recognition of hazardous situations, c) excessive trust induces significant delays in such situations and d) a lack of alarms more significantly reduces trust than false alarms do. Copyright © 2002 IFAC Keyword: Alarm system, Driver behavior, Reliability, Safety, Transportation of cooperation between humans and machines can have a dramatic influence on the performance of the ITS. Previous research has shown that trust in machines is a key factor in attaining appropriate cooperation between humans and machines (Muir, 1994; Muir and Moray, 1996; Riley,1996) . Moreover, trust often determines machines usage (Parasuraman and Riley, 1997; Lee and Kantowitz, 1998) . Humans may not use a reliable machine that is believed to be untrustworthy. Conversely, a machine that is believed to be trustworthy may be relied upon even when it malfunctions. Trust changes dynamically (Lee and Moray, 1992; Muir and Moray, 1996) and has three dimensions, namely predictability, dependability and faith that alter according to humans’ trial-and-error-experiences (Muir, 1987) . Moray, et al. (2000) have shown that a main factor in the development of trust is the reliability of machines. Itoh, et al. (1999) have shown that the dynamics of trust depends not only on the reliability of machines but also 1 Now the author is a doctoral canditate in Research School in Ergonomics and Human Factors, Loughborough University,UK. Copyright © 2002 IFAC 15th Triennial World Congress, Barcelona, Spain on the occurrence patterns of machine malfunctions. Thus drivers’ behavior toward warning systems may alter according to their trust in those systems. This paper examines how, as a result of influencing drivers’ trust in systems, malfunctions reduce the efficiency of warning systems from the viewpoint of a relationship between drivers’ trust and behavior. Moreover two types of malfunctions namely false alarms and a lack of alarms are considered in this study. Because each malfunction presents different phenomena to drivers, each malfunction influences drivers’ trust in warning systems differently. False alarms which produce unnecessarily warnings and frequent false alarms result in a reduction in drivers’ trust in warning systems. Accordingly, drivers may ignore the alarms or temper their reactions to them. Conversely a lack of alarms means that alarms do not issue even though the warning criterion for each systems is fulfilled. Therefore a lack of alarms may result in the absence of any appropriate risk avoidance action when drivers trust warning systems exces-