Evaluating the effectiveness of roadside auditory warnings in tunnel noise: a staged auditory information processing perspective

In tunnels, roadside auditory warnings provide an important safety communication channel for drivers. However, warnings transmitted at the intended volume may not remain clear when reaching drivers. This study examined the effects of broadcast voice, volume, and ambient noise on warning detection, reaction time, speech intelligibility, comprehension, listening effort, and behavioural intention using an audiovisual simulation based on in-situ tunnel recordings. Results showed that the female voice used in this study was associated with better warning detection and speech intelligibility than the male voice. Higher broadcast volume mainly improved detection, whereas high ambient noise reduced speech intelligibility. Speech intelligibility remained low overall and was strongly associated with information comprehension. Higher comprehension was also relevant to higher behavioural intention. Listening effort showed no consistent association with comprehension or behavioural intention. These findings highlight speech recognition as a major limitation and support driver-level evaluation of tunnel warnings.