Accessibility is hard. It’s easy for things to slip through.
Put yourself in the shoes of Logan—a 33-year-old software engineer with red-green colourblindness—rushing for the subway for a conference in an unfamiliar city. They’re glancing about for entrance to the orange line, when they spot this sign (simulating deuteranopia colour-blindness):
Carry many pairs of shoes. It makes it easier to find the cracks.
(Thankfully, there’s an updated version of this sign further along. It’s never too late to improve!)