Once you have as many vehicles in action as you can and you're loading such that you can send a loaded vehicle out as soon as one comes back, then the length of the ride (in distance and time) and the number of vehicles out there on the ride has no impact on capacity as defined as a rate, such as "people per hour."
What affects people per hour once the other parameters are maxed is the dispatch rate. If you're sending out 1,000 people per hour, but double the length of your track... you're still only sending out 1,000 people per hour. There's more people on the ride at one time, so, that measure of 'capacity' is increased, but, the capacity of rate of dispatch is unchanged.
For a coaster, if you can increase dispatch rate if you have shorter blocks because you can send the next vehicle out sooner because the one in front of it has passed a block quicker. If you lengthen the totality of the track, and put in more blocks, but the blocks are still as far apart as before, then you're not sending out vehicles more quickly, you're just increasing the amount of people the ride can hold, not speeding up the number people the ride can process.
To speed up PPH for a coaster you can:
- shorten blocks
- put more people on each vehicle dispatched
- speed up the coaster
- add more tracks
Again, this presumes you're already at a point where each block already has a vehicle and your loading area has enough extra vehicles such that you can dispatch as soon as the first block clears.