Despite rail industry advances in reducing accidents at Highway Rail Grade Crossings (HRGCs), train-vehicle collisions continue to happen. The use of auditory displays has been suggested as a countermeasure to improve driver behavior at HRGCs, with prior research recommending the use of hybrid sound alerts consisting of earcons and speech messages. In this study, we sought to further investigate the effect of auditory variables in hybrid sound alerts. Nine participants were recruited and instructed to evaluate 18 variations of a hybrid In-Vehicle Auditory Alert (IVAA) along 11 subjective ratings. Results showed that earcon speed and pitch contour design can change user perception of the hybrid IVAA. Results further indicated the influence of speech gender and other semantic variables on user assessment of HRGC IVAAs. Findings of the current study can also inform and instruct the design of appropriate hybrid IVAAs for HRGCs.

Highway-rail grade crossings (HRGCs) present multiple collision risks for motorists, suggesting the need for additional countermeasures to increase driver compliance. The use of in-vehicle auditory alerts (IVAAs) at HRGCs has been increasing, but there are limited standards or guidelines on how such alerts should be implemented. In the current study, we sought to investigate the effect of different auditory display variables, such as display type and acoustics, on subjective user assessments. We recruited 24 participants and asked them to rate 36 different IVAAs belonging to one of three display types (earcons—short synthetic tones, speech alerts, and hybrid alerts consisting of an earcon and speech) along 11 subjective ratings. Results showed that a hybrid alert led to better overall ratings for acceptance, safety, and semantic understanding when compared with earcon or speech alerts. Additional analyses revealed that semantic variables, such as speech order and gender, should be accounted for when designing IVAAs in an HRGC context. Hybrid IVAAs with spatial audio showed lower Urgency and Hazard level ratings. Findings of the current study can help inform the design of IVAAs for HRGCs.

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