My understanding that for statistical purposes a vehicle is 'on time' if its 8 minutes late or less. One thing that this chart does not take into account is MAX turn-backs. Trimet control will turn max trains around if they are very late to get them back on time and the max statistics do not reflect the trips that are just skipped completely when a train is turned back. However you know its bad when bus on time performance is the same as light rail on time performance. Light rail is supposed to avoid the delays that the buses encounter. As anybody who has been paying any attention know Trimet light rail service has been very unpredictable lately.