Addressing the Safety of Transportation Cyber-Physical Systems: Development and Validation of a Verbal Warning Utility Scale for Intelligent Transportation Systems

As an important application of Cyber-Physical Systems (CPS), advances in intelligent transportation systems (ITS) improve driving safety by informing drivers of hazards with warnings in advance. The evaluation of the warning effectiveness is an important issue in facilitating communication of ITS. The goal of the present study was to develop a scale to evaluate the warning utility, namely, the effectiveness of a warning in preventing accidents in general. A driving simulator study was conducted to validate the Verbal Warning Utility Scale (VWUS) in a simulated driving environment. The reliability analysis indicated a good split-half reliability for the VWUS with a Spearman-Brown Coefficient of 0.873. The predictive validity of VWUS in measuring the effectiveness of the verbal warnings was verified by the significant prediction of safety benefits indicated by variables, including reduced kinetic energy and collision rate. Compared to conducting experimental studies, this scale provides a simpler way to evaluate overall utility of verbal warnings in communicating associated hazards in intelligent transportation systems. This scale can be further applied to improve the design of warnings of ITS in order to improve transportation safety. The applications of the scale in nonverbal warning situations and limitations of the current scale are also discussed.