Justin F. Morgan

The Effect of Prior Task Loading on Mental Workload: An Example of Hysteresis in Driving

Objective: This study examined how transitions in task demand during a driving and navigation task manifested themselves as delayed adaptation in driver mental workload. Background: A delayed reaction to changes in demand levels, termed hysteresis, has been identified in a number of settings. However, little research has specifically examined the driving task for hysteresis effects. Method: A total of 32 drivers completed drives while using a navigation system that would fail within the drive. Subjective mental workload was recorded prior to and following system failure as well as at the conclusion of the drive. Results: Results indicated that a gradual reduction in overall mental workload across trials and a lagged recovery to reduction in task demand was present within trials. Analysis of the mental workload subscales within trials indicated that this effect was produced by the mental effort component of workload. Conclusion: A moderate hysteresis effect is present in mental workload transitions within the driving task. Although subjective mental workload decreases across trials, the magnitude of the lagged recovery within trials remains unchanged. Application: Scaling of in-vehicle information is beneficial with respect to driver mental workload. Display and communication technologies designers should consider not only the immediate task demand but also the driver’s task demand history when determining what and how to provide information.

The Effect of In-Vehicle Warning Systems on Speed Compliance in Work Zones

The purpose of this research was to evaluate the effectiveness of augmented in-vehicle information on driver behavior in work zones. In-vehicle information systems (IVISs) can increase driver awareness to an oncoming change in traffic flow and provide specific guidelines for driving speed requirements, for example. Three variations of IVISs were examined as the drivers entered a work zone in a simulated driving environment. The first was a control condition, which used only traditional signage and no IVIS. The second condition had the addition of visual in-vehicle warnings and the final condition the addition of auditory in-vehicle warnings. Results indicated that adding in-vehicle warnings did affect driver compliance to the work zone speed limit. Further, participants in the audio warning condition responded more quickly to the warning than in the visual condition. These were each respectively different from the drivers in the control condition. Conclusions and implications are discussed.

Experienced CMV Driver Opinions of Advanced Driving Simulator Scenarios

There is an increasing interest in providing refresher training for commercial motor vehicle (CMV) drivers. Truck driving simulators offer the potential to provide this type of training to CMV drivers in an efficient and effective manner. However, the success of truck simulator-based training depends on drivers’ acceptance of the simulator and scenarios. The present study investigated 48 experienced CMV drivers’ (across three trailer types and two levels of experience) opinion on the realism of 12 emergency maneuvers and 10 extreme conditions in a truck driving simulator. Drivers provided feedback as to the realism of each event in the simulation. Results indicated that, in general, drivers rated the scenarios as realistic as compared to the real-world equivalent situations. There was no pattern of differences between driver experience levels or operation types. These findings have implications for both future simulation-based training programs and future driving scenarios, and suggest that simulation-based refresher training may be accepted by drivers.