Ugh! What happens when you are travelling to a different City? I have seen different rating patterns in different cities where my rating goes up if I am in a ce

Ugh! What happens when you are travelling to a different City? I have seen different rating patterns in different cities where my rating goes up if I am in a certain city for an extended period. So, I would assume that city has on average a higher rider rating. Will they calculate my average from that city's rides? Also, if they are taking into account that city's ratings if I travel to a new country what's the threshold number of rides to calculate my new rating? Will I be randomly locked out of Uber in the middle of night in a foreign city.