I'd imagine this is tracking a medallion number. A day in the life of a taxi, not the driver. A period of slow movement and no fares means the cab is cruising around looking for the next fare and a long period most likely means the cab was back at the garage for a few hours between drivers. I think the program only knows when and where it dropped and picked up passengers so it has to guess everything else. My biggest surprise is how bad they get stiffed on the tips. Or do they?
Might be that cash tips weren't reported. At the last medallion auction they were selling 1 million a piece. Heard there are people who own 30 meddallions. What happens to these people if Uber and other services take over or ubiquitous driverless cars. It's a market ready for massive disruption.