[AnthonyMouse]

You can address things like that with predictive matching. You don't actually wait until there are three rides before matching anybody, you just look at the data for this timeslot and expect that statistically there will be three rides this hour, use that rate based on the drivers who are on, and assign the nearest of the three lowest bidding drivers as they come. If a fourth ride appears that hour then you immediately raise the rate to the fourth lowest bidding driver starting with that ride, and so on, and next time have more data and make a better prediction.