Speed limit is 25- and is strictly enforced by the US Park Police (usually driving white Chevy Suburbans). It’s easy to exceed the speed limit in this area- especially in the straightaways. My girlfriend got out of a ticket when she pointed out a bus (operated by the Park Service) to the officer that was travelling at approximately the same speed for which we were pulled over. Be careful in this area- the officer is overzealous, and he has an attitude.