This exploratory study investigated the effect of cognitive workload on manual lap belt usage in automatic restraint systems consisting of a passive motorised shoulder belt and a separate manual lap belt. The objective of the study was to quantify manual lap belt usage with this type of automatic restraint system under varying cognitive workloads. Ten subjects participated in two testing sessions consisting of a low and high cognitive workload. During each test session, the subjects drove around a pre-defined course where they exited the vehicle at five locations to perform specific tasks. This presented each subject with six opportunities during each test session (start plus five stops) to engage the manual lap belt. Tasks for the second test session were designed with a much higher cognitive workload. Overall, subjects were two to three times more likely not to engage the lap belt under the higher workload test condition. Statistical analysis did not detect any statistically significant differences in belt usage between the low and high cognitive workloads, but the data suggests a trend for decreased lap belt usage under the higher cognitive workload. Safety issues regarding automatic restraint systems are also discussed.
Abstract