Peanuts/Toddler rides- height requirements

Can anyone tell me what exactly are the requirements for toddlers to ride certain rides? Under the kids rides section, it lists some with obvious restrictions, between 36 and 54, or must be over 42, but what about the rides that simply say under 54 inches? I remember hearing that if the child can walk on by themselves, they can ride the under 54 rides, is that true?
Along the same lines, quite a few of the Snoopy rides, such as Peanuts 500 and balloon race say over 42 or with a responsible adult. So, would an 18 month old be able to ride those rides with an adult, assuming she can walk on and sit next to the adult herself in the restraints?

The Guest Assistance Guide goes into detail on those issues starting on page 7.

Yes, as I recall toddlers can ride quite a few of the rides with an adult. Make sure the toddler has appropriate shoes, shirt, and pants.

My recommendation would be to watch a ride cycle before letting them go on the ride. We go in May and the kiddie areas weren't very busy. We let my toddler go on the balloon race with his uncle not realizing that the balloons spin while the ride spins too! He wasn't quite ready for that as a first ride.

If your little one isn't walking look up the handheld infants info on the Cedar Point website- there are quite a few things they can ride with the family.

Thank you both for the info! It was very helpful. I'm personally excited to have another little person around again to ride Peanuts 500 hahaha :) I love that ride!