Switch Root

Randy Weiss found this mathematically significant roadsign in Utah. While descending the mountains via a number of switchbacks he started seeing a pattern. Each switchback had a different speed limit depending on the radius of the turn and the pitch of the highway at that point, and they announce how many more switchbacks to come before you reach the plain at the bottom. With impeccable planning, the switchback 5 from the bottom was given the speed limit of 25 MPH.



The math here is obvious to anybody learning square roots in grade school.

$$\sqrt{25} = 5$$

This sign is found on US-191 heading south to Vernal,