Who sets rider height requirements?

So basicly, the fair is raising the height requirements above what the manufacturer recomends.

I looked up sveral differant parks and fairs, and they do not have a 48" requirement to ride.

This place only requires that the child be 3 years old to ride by themself on the kiddie coaster.

http://www.gradysfunpark.com/rules6.html

This fair only says 54" or less....

http://www.wadeshowsinc.com/attractions/kiddy.asp

Dorney park says under 54"

http://www.dorneypark.com/public/inside_park/rides/all_rides.cfm

Wisdom, the company that builds the ride does not list the recommended height requrement on there site.

http://www.wisdomrides.com/catalog/?page=shop/flypage&product_id=25&category_id=886336ece89dd294d86207280dc8e27b

Back in 2006 Waldameer's Scrambler was the 36" to 48" with an adult requirement. On our first trip there in 2007 we were about to get in line when I noticed the sign said "must be 48 inches tall to ride". I waited for the cycle to stop and checked with the ride op and she confirmed it, nobody under 48". Last year it was back to the 36" to 48" with an adult rule.

Tom