My son is with them and there are a lot of restrictions. You are marked down for journeys between 11pm and 6am. You are marked down for journeys of less than a mile or less than 5 minutes or more than one hour. There is also a limit on how many journeys you are allowed each day before being marked down, around 5/6 journeys. A journey ends when the engine turns off.
They are also very strict on smoothness so any acceleration or sharp braking is marked down.