DS is 39.5 without shoes,will he make it on 40" rides??

[EmptyCinema]

Here's how all of this work. The ride designers design a ride and say "you must be 38" tall to safely ride this ride" (because of the restraints, or otherwise). Disney Legal/Management fudges this number and the ride becomes say 40". (I don't know the real margins, these are guesses). Yes, a 39.5" tall guest would be "fine", but that's not the CMs place. His job is to ensure rider safety by following the guidelines established by Management. It's not a question of that .5 being safe, but the problem is, if you allow a little leeway on the heights, where does it stop? Is 39" ok? 38.5"? 38"? They've drawn a line they have to stick to.

 

[dqpowell]

then why doesn't disney just say 39.5 if it doesnt make any difference??

Small differences will not have a significant impact. Large differences will. As somebody else explained, the figures have a fudge factor built in... if it were truly unsafe for somebody 39.5" to ride, then the minimum required height would be set a couple inches higher just to be sure, such as 42" or 43". Disney would not risk the safety of guests by setting the minimum height requirement to the true bare minimum for safety.

It's the same way with any engineering task. If the minimum necessary tensile strength for a support cable on a bridge is 1500 lbs, they will specify something like 2250 lbs or more, depending on the application.

You should also understand that sometimes the minimum height requirements have nothing to do with safety, but are used as a way to keep children considered too young for a particular attraction away. Since Disney can't easily determine a child's age at the entrance to an attraction, they use something they can easily check -- height -- as an imperfect but better than nothing indicator. They changed the minimum height requirement from 35" to 40" at Stitch's Great Escape a while back. This had nothing to do with safety, but everything to do with the fact that parents complained their young children were scared by it.

David