In the United States, it's incredibly frustrating that you have a train that leaves for Penn Station at a certain time. If someone turns up early and goes and sits in an unoccupied seat, you're actually improving the capacity of the line. Now, allowing people to travel late is slightly dubious because obviously you don't want that to happen but there are empty seats on a lot of trains going from those two cities during the day. It reduces... And yield management practice.