As a passenger I have noted on the passenger app that it will say "on a trip" or "trip in progress" . I noted this once as a passenger long before the driver picked me up , sure enough when I got in the car he had already started the ride. I cancelled that ride and complained to Uber because he had started that ride long before he picked me up- he was scamming the system. As a driver it is my preference not to start the trip until they are all safely tucked into their seatbelts, we have hashed out a general destination and I have a feel for the general attitude of the riders, all of which must meet my expectations before I start the trip. If anything comes up within that first 30-60 seconds that doesn't feel right, like extra passengers, stops at Taco Bell or a piss poor attitude then - I cancel the trip and ask them to exit my vehicle. Overall, I rarely have any issues, I pull up, pax get in, I get an address and I drive to destination. The End.