From Mackworth’s clock to the open road: A literature review on driver vigilance task operationalization

Objective
This review aimed to characterize tasks applied in driving research, in terms of instructions/conditions, signal types/rates, and component features in comparison to the classic vigilance literature.

Background
Driver state monitoring is facing increased attention with evolving vehicle automation, and real-time assessment of driver vigilance could provide widespread value across various levels (e.g., from monitoring the alertness of manual drivers to verifications of readiness in transitions of control between automated and manual driving). However, task requirement comparisons between the classic vigilance research and vigilance in car driving have not to date been systematically conducted.

Method
This study decomposed the highest-cited vigilance literature of each full decade since the 1940s for the situational features of the renowned vigilance decrement phenomenon originating from Mackworth (1948). A consensus set of 18 different situational features was compiled and included for example an (1) isolated (2) subject … perceiving (3) rare (4) signals … against (10) frequent (11) noise … in a (17) prolonged (18) task. Next, we reviewed 69 experimental vigilance task operationalizations (i.e., required signal detection and response) within 39 publications concerned with driving vigilance. All vigilance tasks were coded as “driving vigilance tasks” or “non-driving vigilance tasks” based on the perceptual signal and response action both belonging to normal driving activity or not. Presence, absence, and unreported presence/absence of each of the 18 features was rated for each task respectively as “overlap”, “contrary”, and “unspecified”. In conjunction, instructions/environmental conditions, signal definitions, signal rates, and summaries of the experimental vigilance tasks were extracted.

Results
A majority of driving vigilance tasks was performed in simulators (69%) compared to on-road (28%) and watching videos (3%) along with large differences in task conditions. Participants had to maintain fixed speed/lane positions in the simulators in higher proportion (74%) than on the road (36%) where they had only to drive “normally” and/or by loose conventions like “according to the law” more often (55% versus 15%). Additionally, presence of other traffic was found more often on-road (91%) than in simulators (48%). A specification of signals to detect and react to was found present within/for driving less often (59%) than alongside/in conjunction with driving (100%). Likewise, rates of signals (i.e., frequency of signal occurrence) were reported more often for non-driving vigilance tasks (80%) than in driving vigilance tasks (21%). For driving vigilance tasks, the highest overlap was 12 of the 18 features present (67%). On average, results showed relatively low levels of classic feature overlap (36%) with high rates of unspecified feature presence (46%) for driving vigilance tasks compared to non-driving vigilance tasks with higher classic feature overlap (64%) and fewer features unspecified (13%).

Conclusion and application
There is little overlap between the well-known and often cited vigilance decrement phenomenon and published experimental tasks of driving vigilance. Major differences were also found in the instructions/environmental conditions of simulator versus on-road experimental driving vigilance tasks. What driving vigilance practically is in the real-world thus remains a promising area for future research. We recommend that researchers apply approaches which account for more real-world driving features to better expose and address uncertainty regarding driving and vigilance.