Therefore the loremasters of Men said that a Straight Road must still be, for those that were permitted to find it. And they taught that, while the new world fell away, the old road and the path of the memory of the West still went on, as it were a mighty bridge invisible that passed through the air of breath and of flight (which were bent now as the world was bent), and traversed Ilmen which flesh unaided cannot endure, until it came to Tol Eressëa, the Lonely Isle, and maybe even beyond, to Valinor, where the Valar still dwell and watch the unfolding of the story of the world.
– The Silmarillion, Akallabêth
From the Grey Havens the Eldar ever and anon set sail, fleeing from the darkness of the days of Earth; for by the mercy of the Valar the First-born could still follow the Straight Road and return, if they would, to their kindred in Eressëa and Valinor beyond the encircling seas.
– The Silmarillion, Of the Rings of Power and the Third Age
The Straight Road literally coalescing only at the Elves’ need would be a pretty neat solution to keeping
the entitlement-complex plagued Men off it. More effective than a simple old sign could dream of achieving anyway.