I'd call it more "busy compared to other days in May" but it certainly isn't nearly anything as bad as July 4th or most of August. Really, unless you're looking all that much, you don't notice, because around that time of season all sorts of school trips are going on. The only reason you notice that it's Physics Day is that all the kids are doing work and carrying notebooks/calculators/equipment, rather than just riding!
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PO!NT OF VIEW - A Different Look at Roller Coasters
http://www.crosswinds.net/~justmayntz/thrills/