Can't create enough ride vehicles?

I'm playing RCT and I close a ride after it breaks down. I try to reopen it but it says "Can't open: can't create enough ride vehicles." Huh? I tried testing it and closing and opening again but it wouldn't work. So I deleted it and built a new ride, tried to test and it said the same thing. I closed another ride and tried to open it but I got the same message. Is there anything I can do? Please help.

You have too many people/rides operating at your park. Do a search, you'll find many, many, MANY topics about it here...

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Whenever you can ride a roller coaster and experience 15 spots of intense airtime, you know you're on a good coaster. (see: Phoenix)