多谢信息，另外才发现这个：
Family/Group: Up to seven people with a maximum of two adults arriving at a national park in a single vehicle or visiting a national historic site together.
记得之前去看过park canada的网站，不是这样定义的，没限制大人人数，不知道你们买的什么票，是最近刚生效的规定吗？
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just called park canada Calgary Office 1-800-748-7275, the lady said there are no limit for adults. Don't know why they put this online.