Effective cues for accelerating young drivers' time to transfer control following a period of conditional automation

During conditional automated driving, a transition from the automated driving suite to manual control requires the driver to take over control at a moment's notice. Thus, it is critical that a driver be made situationally aware as quickly as possible in those conditions where he or she may not be paying full attention. Recent research suggests that specific cues about upcoming hazards (e.g., "crosswalk ahead") can increase the drivers' situation awareness during these safety-critical take-over situations when compared with a general cue ("take over control"). The current study examines whether this increased situation awareness which occurs as a result of more specific cues translates into improved hazard mitigation performance within the same limited time window.

Fifty-seven drivers were randomly assigned to one of five between-subjects conditions (one control condition and four experimental auditory cue conditions) that varied in the specificity of information provided about an upcoming hazard. The four experimental conditions included a period of conditional automated driving where the driver was engaged in a driving-irrelevant task and looked away from the forward roadway prior to a take-over request. Drivers in the fifth condition had no cue and drove manually throughout. The same six simulator scenarios were used in all five conditions to evaluate how well the driver mitigated a hazard. The average velocity, standard deviation of velocity, and average absolute acceleration were recorded along with the glance behaviors of drivers.

In general, during the 4s prior to a latent hazard (following the alerting cues in the automated driving conditions), the more likely a driver was to glance towards a latent hazard, the more likely the driver was to reduce his or her speed. Moreover, analyses focusing solely on hazard mitigation behavior revealed patterns that mirrored the glance behavior results. Specifically, drivers that were presented with cues that described the environments in which hazards were likely to occur were more likely to demonstrate vehicle behaviors that were consistent with speed reductions (lower velocity, higher speed variability, and higher absolute acceleration) than were drivers who were presented general cues or cues about the identity of the upcoming hazards.

Even in as little as 4s prior to a potential hazard, cues that inform the driver of the environment in which the hazard is likely to occur increase the likelihood that the driver mitigates the crash compared with drivers who are provided general information or threat identity information.