With over 2000 people on some rides it is getting a bit crowded on my screen, I would like to suggest two alternatives to help the situation:
Segregate the rides by server farm i.e. have a server farm for each of London, Watopia abd Richmond and have riders pick which they want on login. Those who want a less crowded venue can pick a ride with less riders, this one would also help the riders who dislike one ride for some reason.
Have a set of filters in settings that let clients filter out some riders based on predefined criteria such as geographical location or members of a group etc …