InterDynamics’ scientific advisor (and from whose thesis FAID came out of) Dr Adam Fletcher has indicated the following:
The subjects in the studies that were done when FAID was developed worked in a range of operations with various commute times as occurs in most companies and industries. On average, the commutes were 30-45mins each way. This time period is not a separate inclusion within FAID, but rather reflects the living conditions/situation of the people involved in the scientific research project. Thus long commutes have come to be defined as those longer than 45mins.
Around 30mins each way in terms of FAID, has come to be considered ‘normal’ and anything significantly over 30-45mins is likely to mean FAID is underestimating the impairment and overestimating the recovery sleep. The resolution is not so high however that we should get caught up about 5 or 10 mins in commute time when we know other factors (such as how boring/monotonous the drive is, the time of day of the commutes and the conditions) all play a role as well.
Where significantly longer commutes exist at the start or end of shifts, then the shift start/end time can be extended to account for the extra time above (say) 45 minutes, to review the impact on fatigue exposure as a result of the longer commutes.