One-man operation is the industry standard practice for regional and commuter services. However that isn’t the case for Denver RTD — which still uses both a driver and conductor:
Recent staffing issues for the Regional Transportation District’s (RTD) University of Colorado A-Line have caused cancellations of trips, leaving travelers waiting at Denver International Airport (DIA) for hours. Since January, 1,548 A-Line trips have been canceled, according to data from RTD. About 80% of those cancelations – 1,290 in total – happened because there wasn’t a second crew member available to be on the train. One reason for this is that the A-Line requires two people to be on board the train during a trip.
Thanks to automation, two-man operation became obsolete decades ago. To make matters worse, RTD work-rules require the second crew member to be an armed guard (i.e. rent-a-cop) — which limits the pool of applicants.
Systemic Failure 