it's extremely unforegiving. even when everything goes correctly, we experience a lot of challenges. we have five routes that show a single trunk. we're one of very few systems that goes from mixed traffic on the surface to a dedicated automatic train control system in the subway. we have three lanes that turn around add embarcadero where we only have two turnaround slots. so if we slip our turnaround time by 30 seconds or a minute, the delays propagate through the whole system. we also run frequent service and are living right now with an old train control system. as you know from previous issues we're working with old train and those work against us as we deliver day to day service. the sources of delay are spread in a number of areas. our largest number of incidents are related to the train control system. that includes a train that is in automatic mode and it includes when we have disturbed segment clocks or segments of the subway where no train can be in automatic while [indiscernible] is the largest number